I think they are a flash in the pan of sorts. By sorts, I don't think they will become a powerhouse year after year. However, I feel like they will become the next Louisville. A few years they will have championship seasons, more than most they will have fairly solid seasons (8-9 wins), and every now and then they will have mediocre seasons.
I come to this conclusion based upon a couple of things. I still think they will lose most of the blue chip talent to UF and FSU. Every few years they should expect to have a solid team and a few unheralded recruits turn into major stars (like their QB and some of their defensive players this year). However, there will also be years when the talent just isn't there and no diamonds in the rough emerge. Their coaching is top notch for now, but I wouldn't be surprised to see them move on to bigger and better jobs. Most of the time when coaches leave it creates problems and USF should be no different (i.e. this year's Louisville) And finally, their conference is weak enough for them to go to a bowl almost every year.