> These projections do not account for increase in life expectancy.

That's inaccurate. The study in the link, which has those predictions:

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

See the Mortality section.

Yes, India will peak at 1.7 billion, but then begin to decrease. That peak happens in 2050, which is closer to our 2020 than 2100.