Upvote:2
There is no guarantee that the remaining passport will be returned by your travel date (nor indeed does the email youβve received guarantee that the other visas have been approved - see for example What does this mean? "Your UK visa application has been issued")
The UK specifically advises applicants not to make travel reservations until the visa decision is known. Flight and hotel booking documents are therefore not required when submitting the application (unless youβre applying for a transit visa). See Section 4 https://www.gov.uk/government/publications/visitor-visa-guide-to-supporting-documents/guide-to-supporting-documents-visiting-the-uk
Itβs up to you whether you hang on and hope to receive all the decisions in time for the original travel date, postpone the trip, or cancel it until you know the application outcomes.