He's started his entire career....won 2 Super Bowls...you think he'll want to sit behind a rookie as an insurance policy?
First he'll want to get paid and second he'll want a legit chance to start. Otherwise he'll retire if the Giants cut him and his $15M salary.
The guys to watch in the offseason are in Minnesota. All 3 (Keenum, Bridgewater and Bradford) are free agents in 2018. Minnesota most likely can only keep 1, but the other 2 will probably want starter money too somewhere.