Sorry LO, title of this thread is 'Why is the RAF buying the F-35?' not 'The Future of F-35' or 'India's Fighter Procurement Aspirations'. There are other old threads for such non-objective analyses.
Many, pre-PAK FA/J-20, would have also said:
F-22 for the USAF?
Too much technology, too few airframes.
Perhaps not any more.....
So, what will the future of Typhoon be circa 2020?
Likely won't see many (if any) post 2030. Tranche 3 (sans AESA) will find itself towards the back of the pack 2020-2030.