He's only 26, that's got to be at least 5 years and maybe 7+ if he holds up. He does rely on athleticism and he takes a pounding every game, you could be right.
Not commenting on trade, just that he is youngish.
Isaiah turns 27 this season (actually, he turns 27 on Sunday).
If you look into the annals of NBA history, you'll be hard pressed to find a tiny score-first guard like Isaiah who lasted beyond his 31st birthday.
I'd say, best case scenario, Isaiah has four seasons after this one playing anywhere near his current level. If he's still in the league at age 31/32, that will be a significant accomplishment.