Interesting and tough question to get a grip on! Normally you would expect the focus to have shifted to the candidates by now...but the Demorats hate for GWB is so deep and ingrained (and pathological) that it hasn't happened.
I suspect Thompson won't become a focus for the Democrats until, when and if, he becomes the Publican front runner..which should be about 5 ms after he announces. It will happen because Thompson would thrash O'bama easily and is, and they know it, more than a match for Clinton. I don't think they feel, rightly or wrongly, that any of our present candidates represent an existential threat to either of their frontrunners.
I'd say you're pretty much right on. There are a few lefties who are beginning to sense that Fred is a real threat(eg. Bob Beckel), but I think most of them are still assuming it'll be Rudy McRomney. Letterman, for example, is still picking on Romney.
It is amazing to observe the pathological hatred of the left for the very moderate and the very "lame-duckian" George Bush. It makes one wonder what they would do in the face of a true Conservative.