Depends on what you mean by "legit contender." I don't think Tennessee will ever be an every-year contender for a CFP berth like Alabama and Ohio St currently are. I do think that Tennessee is a good enough program to vie for a CFP berth something like once every 4-6 years, and be competitive in conference all the other years.
I do question why a school like Clemson in particular can turn into an every-year contender for the CFP and Tennessee could not, though. Clemson does not have the tradition and history that Tennessee does and both schools have to go into other states to recruit. Clemson still brings in less revenue than Tennessee does from football. If Clemson can be in the playoff 3 years in a row, why couldn't Tennessee do that at some point in the future? There was a time when general thought was that Clemson in any given year will be in the ACC pecking order behind Florida St, Virginia Tech, and sometimes Miami.
I mean, read this blurb from this article (
Five Prominent College Football Coaches On the Hot Seat For 2011) about Dabo in 2011. My how times have changed.