It was possible to enter India with a new passport and the valid visa in the old passport last year. However I can't get any official confirmation on the current status.
Notably, Timatic used to explicitly say that "Valid visas in expired passports are still acceptable, provided accompanied by a valid passport of the same nationality of the expired passport", but currently it doesn't seem to say it anymore. I've checked United one.
Indian consulate in Chicago says:
Transfer of visa to a new passport is not needed in emergency and the applicant can travel to India with old passport having Indian visa, along with new current passport.
Emphasis is mine. I do not have an emergency, and in any case I wouldn't trust embassy web sites as they update very slowly.
So anyone flew to India recently with a visa in an old passport? Was there any hassle/issues during checkin or immigration in India?
I'd transfer the visa, but the process is incredibly annoying, and paperwork-wise is the same as getting a new visa.
Update: things get more interesting. Apparently there seem to be two different versions of TIMATIC.
For example, one from KLM has this exact wording:
... This does not apply to passengers with a PIO card.
Valid visas in expired passports are still acceptable, provided accompanied by a valid passport of the same nationality of the expired passport.