I think that this would be possible yes, although I wouldn't be surprised if we soon see the turret blacklisted from the grinder and perhaps other mob killing devices. If it is possible to have the turret killable by the grinder but it doesn't drop another turret then I hope that is the path taken. Turrets are practically renewable anyway with a golem farm, a witch farm and an obsidian generator so creating an infinite supply is not impossible (and maybe a bit more fun than recycling the same one over and over again, just my opinion though).
I can't be the only one who wants to set up a turret manufacture and redemption line. (In 1.5 I tested the ability of a turtle to place a turret on a conveyor belt, successfully)