Upvote:1
There is an arahant called metteyya and for the buddha it is Dn26 https://suttacentral.net/dn26/en/sujato#dn26:24.6 https://suttacentral.net/define/metteyya
Generally speaking people love backgrounds stories of the buddhas and the theravadans have invented those stories and put them in KN, instead of polluting the suttas with that, contrary to the people who invented Mahayana who mixed them with their suttas.
Upvote:3
How did this idea of next Buddha formed? Is it the influence of other religion where they say Kalki or Christ will return.
No need for outside influence, just simple logic. It doesn't make any sense to have only one single Gautama Buddha arisen in a universe (or multiverse) with unfathomably long history without descernable beginning and end.
Also does Pali Canon mention many other Buddha before Gautam Buddha?
Yes, see the Buddhavamsa, the 14th Book of the Pali Canon's Khuddaka Nikaya for the list of 24 Buddhas predecessors to Gautama Buddha. See DN 26 for infos. on Metteyya, the future Buddha.