What did Hitler say in Mein Kampf about the possibility of other nations allying against Germany in response to her aggression?

In Mein Kampf as well as in Zweites Buch, Adolf Hitler advocates the idea of securing Lebensraum ("living space") at the expense of other nations in wars of aggression. His substantiation, as far as I remember, is that the ultimate goal of any Volk (a people/nation) is to survive and that land is needed for better development of a Volk and, in particular, to improve its resources and population, which are needed for survival.

That is, in so far, a good summary. However, it is not complete, and lacking some crucial observations.

Hitler didn't talk about ever-increasing "Lebensraum" per se, as in "total world domination". An oft-repeated, but quite limited and flawed interpretation of Hitler's geostrategic outlook. He might have been somewhat crazy by our modern standards, but he wasn't a raving lunatic (...at that point...). He had quite clear ideas of what the "sunny path" of his politics would look like, and that was "limited" (if one could use that word in this context) to Europe.

The idea was

1. winning "Lebensraum", and
2. defeating the "jewish Bolshevization of the world".

Both goals were to be achieved in the east, i.e. Russia, specifically.

Let's dig through his ramblings in "Mein Kampf" and shine some light on a couple of key points.

Talking about pre-WWI politics, he notes that there are only two ways Germany could achieve power (page 154, translation and emphasis mine):

Wollte man in Europa Grund und Boden dann konnte dies im großen und ganzen nur auf Kosten Rußlands geschehen [...]. Für eine solche Politik allerdings gab es in Europa nur einen einzigen Bundesgenossen: England.

"If one would want land in Europe, this could only happen at the expense of Russia. [...] For such a policy there was, however, only one ally in Europe: England."

He rambles on a bit, and then posits the other possibility (page 156f.):

So blieb also noch die vierte Möglichkeit: Industrie und Welthandel, Seemacht und Kolonien. [...] Nein, wenn wir diesen Weg beschritten, dann mußte eines Tages England unser Feind werden.

"So what remained was the fourth way: Industry and global trade, power at sea and colonies. [...] No, if we went down this road, England had to become our enemy one day."

He concludes on page 157:

Wenn europäische Bodenpolitik nur zu treiben war gegen Rußland mit England im Bunde, dann war aber umgekehrt Kolonial- und Welthandelspolitik nur denkbar gegen England mit Rußland.

"If european land policy was only achievable against Russia, allied with England, then on the other hand colonial and world trade policy was only thinkable against England, allied with Russia."

This, however, were reflections on the pre-WWI situation. Later on, with Russia ruled by Bolshevism, Hitler only saw one option remaining. Page 753:

...trotz alledem hätte es vor dem Kriege auch noch den zweiten Weg gegeben, man hätte sich auf Rußland zu stützen vermocht, um sich gegen England zu wenden. Heute liegen die Verhältnisse anders. Wenn man vor dem Kriege noch unter Hinabwürgen aller möglichen Gefühle mit Rußland hätte gehen können, so kann man dies heute nicht mehr.

"...for all that, prior to the war there would have been the second path, one could have relied on Russia to turn on England. Today the situation is different. While, prior to the war, one could have swallowed all kinds of emotions to ally with Russia, this is no longer possible today."

At this point (and quite a bit later still), Hitler was under the impression that he might win England as an anti-Bolshevism ally. Page 755:

Ich möchte diese Betrachtungen nicht beenden, ohne nochmals auf die alleinige Bündnismöglichkeit hinzuweisen, die es für uns augenblicklich in Europa gibt. Ich habe schon im vorhergehenden Kapitel über das deutsche Bündnisproblem England und Italien als die beiden einzigen Staaten in Europa bezeichnet, mit denen in ein engeres Verhältnis zu gelangen für uns erstrebenswert und erfolgverheißend wäre.

"I do not want to finish these observations without pointing out one more time the only alliance open to us in Europe at the moment. I have already mentioned in the previous chapter, about the German alliance problem, England and Italy as the only states in Europe with which a closer relationship would be desirable and promising for us."

He then goes on with a bit of wishful thinking how such an alliance with England would put an end to the entente and isolate France.

Damit aber würde der Bund Deutschland die Möglichkeit geben, in aller Ruhe diejenigen Vorbereitungen zu treffen, die im Rahmen einer solchen Koalition für eine Abrechnung mit Frankreich so oder so getroffen werden müßten.

"This alliance would give Germany the opportunity to make those preparations at leisure which would be necessary either way in the context of such a coalition to settle the score with France."

He summarizes on page 757:

Nicht West- und nicht Ostorientierung darf das künftige Ziel unserer Außenpolitik sein, sondern Ostpolitik im Sinne der Erwerbung der notwendigen Scholle für unser deutsches Volk. Da man dazu Kraft benötigt, der Todfeind unseres Volkes aber, Frankreich, uns unerbittlich würgt und die Kraft raubt, haben wir jedes Opfer auf uns zu nehmen, das in seinen Folgen geeignet ist, zu einer Vernichtung der französischen Hegemoniebestrebung in Europa beizutragen.

"Our future foreign policy may not be western or eastern orientation, but eastern policy in the sense of acquiring the necessary land for our German people. As this requires strength, but the mortal enemy of our people, France, is strangling us remorselessly and robbing us of strength, any sacrifice is necessary that would contribute to an annihilation of the French hegemonic ambition in Europe."

He believed that England would be willing to abandon its Entente allies, indeed that England would not be that interested in defending France (let alone Poland). Page 764f.:

In England war mit der Vernichtung Deutschlands als Kolonial- und Handelsmacht und dessen Herunterdrückung in den Rang eines Staates zweiter Klasse der Krieg wirklich siegreich beendet. Ein Interesse an der restlosen Ausmerzung des deutschen Staates besaß man nicht nur nicht, sondern hatte sogar allen Grund, einen Rivalen gegen Frankreich in Europa für die Zukunft zu wünschen.

"With the destruction of Germany as a colonial and commerce power, and its suppression into a second-class state, the war had indeed ended victorious in England. There was not only no interest in destroying the German nation root and stem, there was reason to wish for a future rival to France in Europe."

We know this turned out to be wishful thinking.

To summarize in my own words:

Hitler's idea was to win Lebensraum at the expense of Russia and its satelites specifically. This, by necessity, required neutralizing France.

Hitler indeed was under the impression that it would be possible to win Italy and England as allies for such an undertaking.

He was expecting France to be opposed to any German rise to power, and planned on taking out that threat to his flank -- while not expecting opposition from England. An assumption mostly based on "they are a Germanic people as well", and "they don't like Bolshevism either".

As for how things would have went on after a successful war, in Hitler's mind, we have to look no further than his "political testament". Page 754:

Duldet niemals das Entstehen zweier Kontinentalmächte in Europa! Seht in jeglichem Versuch, an den deutschen Grenzen eine zweite Militärmacht zu organisieren, und sei es auch nur in Form der Bildung eines zur Militärmacht fähigen Staates, einen Angriff gegen Deutschland und erblickt darin nicht nur das Recht, sondern die Pflicht, mit allen Mitteln, bis zur Anwendung von Waffengewalt, die Entstehung eines solchen Staates zu verhindern, beziehungsweise einen solchen, wenn er schon entstanden, wieder zu zerschlagen.

"Never suffer a second continental European power to arise! Consider any attempt at organizing a second military power at Germany's borders, even if just the formation of a state capable of generating military power, an attack on Germany; and see in it not only the right, but the duty, to prevent the formation of such a state, or if already formed, its annihilation, with all available means, including force of arms."

So, the idea was to neutralize France, smash Russia (and everything in the way of that goal, like Poland), annex whatever eastern territories might be deemed necessary, and then make sure that Germany remained the only significant power in Fortress Europe -- assuming that England would be satisfied to retain its overseas empire.