I don't think it's utterly unreasonable to be a bit exuberant about Middlebrooks at this time. It's clear that he hasn't finished growing into his toolset. As he is right now, he has everything he'd need to develop into a highly talented third baseman, and as young as he is, at the level he's playing, not that unreasonable to project him to add some growth on top of that.
Sure no one's ever going to let me live Anderson down (although he does still have time, and is coming around), but the fact is the Sox have a pretty good batting average when it comes to developing prospects and getting them ready to produce so I'm willing to go out on a limb and say that I like Middlebrooks' chances to succeed too.