He'll eventually get there
But in terms of QBs I wouldn't say a top 16 rank is beyond him at this point. I'd rank the following ahead of him:
AFC East: Brady
AFC North: Flacco, Big Ben
AFC South: Schaubb
AFC West: Rivers, Manning
NFC East: Vick, Manning, Romo
NFC North: Cutler, Rodgers, Stafford
NFC South: Ryan, Brees
NFC West: Smith
That's a total of 15 starting QBs who I'd rank as better than Tannehill at this stage in his career, and when he does start making the big plays in games he could certainly push himself ahead of some of those names listed above. The lad has a high ceiling, and under the right coaching, and with the right players to work with, the lad could in time make himself into a solid top ten QB in the league.
andrew luck.