Cancellara could improve in the mountains if he dropped weight, BUT he would never climb like Contador, Pantani, etc. His style would me more like Ullrich or Indurain, using all his strenght without getting out of the saddle.
The 2010 TdF is going to be great. Contador is the man to beat, but I wouldn't rule Lance out. This year he had a broken collarbone and rode the Giro first, while Contador and the Slecks didn't.
For 2010, he has announced that he will not be riding the Giro, so it is clear that Lance is going back to the old days trainning, focussing exclusively on the Tour.
Regarding Contador I still think he is much better climber than Time trialist. Yes, he beat Cancellara in the last TT of the TdF. But remember that it was not a flat TT, it had a climb at the beginning. On top of the climb Contador had 40 seconds over Cancellara, and at the finish line that difference was reduced to only 2 seconds. Cancellara cut the difference (38 seconds) in the last part of the TT. On a flat TT he is not the best, he simply doesn't have the big body frame of Indurain, Ullrich, or Cancellara and never will be at that level in my opinion.
In the monuntains however he is pretty much unbeatable. Do you guys think he will ever beat Pantani's record on Alpe D'huez??