i think 4++ gen fighters will remain relevant up until 2060s (germany will operate EFTs) . Once the TF project matures and comes into service with TAF, it will be a candidate for 5th gen fighter procurement.
Germany is not a good example as they are buying more EFTs to support their industry and not because it is the most capable platform available - F-35As are way better.
Germany will start inducting the 5/6th gen FCAS from around 2040, which is it co-developing with France.
J-10C is probably a little late now and so BD should set its sight on the J-35 that should be available in the latter half of this year.
Western 4+ gen now(EFT?) for Myanmar and then best to jump onto Chinese 5th gen latter half of this decade to deal with India.
Anyway Western is not reliable against India at all as we just saw with the favours given to India as regards travel restrictions by both UK and USA, that neither BD or Pakistan got. Brexit UK is begging India for a trade deal right now.