Jack's been an underwhelming NBA athlete for years now. It can be masked if you play him at the 3, but his natural position will always be the 2.
His game has never been predicated on quickness or athletic ability (which is somewhat rare among guards). In that aspect, he'll be well equipped to adjust as he gets older. However, there will be games where his opponent at the 2 is simply quicker and the team defensive concept will need to change in order to deal with that.
And, as we've seen in the past 2 games, you can't play him 40+ minutes every night and expect him to hold up as well as a 26-year old. The guy will be 32 in a couple weeks. Something that does play into longevity-related questions: he's played a relatively small number of games compared to other players his age.
I've got a few qualms with your list, though:
Turkoglu was never good enough to "fall off," and he has fallen off this season. He parlayed a couple decent seasons with Dwight Howard into a ridiculous contract and is clearly overrated. Hamilton isn't quite the same player he was and is ideally suited for a Ray Allen role. Baron Davis has fallen off. Ginobili's battled some injuries as of late (and being an international player, he has a lot of basketball wear and tear).