MKI is getting old, and we may have to search for proer replacement for mki from 2040 or 45 onwards. Proper replacement means a new aircraft with similar endurance &payload capacity.
Will AMCA fit in to that mki box? I dont think so. Snd we all saw how reluctant was IAF initially with LCA due to its endurance & payload limitations.
The era of heavy or medium or light is gone.
IAF wants mwf type range so that it can swing between China and Pakistan frontier in case of two front action. Payload of lca is sufficient for most cases.
By2040 I think unmanned UCAV will do the risky jobs such as bombing . So no need for heavy manned jets. 5-6th gen jets will evolve as system of systems with lot of unmanned drones both small and big in network with them. Aura and other stealth drone will penetrate e emeny air space.
Most probably su30 replacement will be optionally manned bigger version of AMCA which could come by 2050. That's all too far out. Right now we are still building su30 which with mid life upgrad keep serving till 2060!!