Oh he definitely will stay in the OF. It's a point of pride for Bautista, I bet. He takes great care of his body and he probably has every intent to stay in RF until he retires.
It's also the norm in baseball. Veteran outfielders like Marlon Byrd, Torri Hunter, Jayson Werth, and Carlos Beltran stay in the OF, even if their defense slips. Elite veteran players just don't typically switch positions, unless it's from C-->1B or maybe 3B-->1B mid career if they outgrow the hot corner. Taking a player and forcing a late career position switch is a good way to f*** him up (Hanley) or neuter all of his value (Mauer). The only positive precedent that I can think of from recent memory is Cruz shifting to partial DH duties this year with good results.