Well, considering Ted Thompson has been the GM for only two years going on three, and the 2007 Packers that went 13-3 were mostly comprised of Sherman's guys, I don't think you can claim that Thompson is that great of a GM yet. We really haven't seen any of his guys come to fruition yet.
Drafting the best guy available just because he's the best isn't a very intelligent thing to do. None of the great GM's follow that philosophy.
The Packers won't be a contender next season. They'll lose the division to the Vikings. Probably have the second best record in the division and make the playoffs, but Favre retiring just strengthens the Giants and the Cowboys in my opinion. In all honesty, I could see them missing the playoffs if they don't win their division. The Saints are going to be better, and the Bucs probably won't get any worse.
Speaking of Colt Brennan, I can help but think he is completely overrated. He was good at Hawaii, but he didn't play any good teams. When they finally plaed George (a pretty decent SEC team) they were crushed 41-10 in the Sugar Bowl. He went 22/38 for 169 yds and 3 ints. I watched him pass in the senior bowl and he looked like crap too. The problem is this years draft isn't stocked with decent QB's.