Through the magic that is Pro-Football-Reference, we can start to find players that were similar to Alex Smith, and in doing so, a very interesting name pops up: Carson Palmer. My guess is that off the bat you don't believe me, so let me explain. Last season, Smith was 25 and completed 60.5% of his passes, 4.8% of his passes were TDs, only 3.2% of his passes were interceptions and he threw for 5.8 yards per attempt (adjusted yards of course) while, when he was 25, Palmer completed 60.9% of his passes, 4.2% of his passes were TDs, 4.2% were interceptions and he threw for 5.7 yards per attempt (see table below). These are not cherry picked stats either, as across the boards, they are incredibly similar (except of course on interceptions where Smith was much better). So perhaps Smith will not end up as another first pick bust, but rather just a late bloomer.
It is possible of course the similarity between Smith and Palmer is just a coincidence and that this small sample analysis is totally unreliable. To check that, we go back to PFR and check on other 25 year old QBs that have had similar performances. The list is actually pretty impressive and includes Bledsoe, Cutler, Lomax, Carr and Marino. The list also includes JP Losman, so Smith's future is not a lock.
It does however, look like Smith has a real shot if he is given some stability in the coaching situation and remains healthy.