At the same time, the PAKFA would be a new aircraft while the F-22 airframes would be at least 5 to 10 years old. Would the USAF be able to maintain aircraft availability rates at high enough levels to provide that quantitative advantage? The 95%+ availability rates for the F-15 and -16 in GW1 came about partly because non-mission capable aircraft deployed in the war could be replaced from a much larger fleet afterall.
Also, India is much closer to the Russians than they are to the US, historically. We have a common adversary in China, but there are some situations over which we differ i.e. Pakistan.