Yeah, as of right now, Evans is in the best position to win the tour, based on his current place in the overall classification (3rd, 2:06 down) as well as his better time trialing: in 2007, for example, he was second in the final day's time trial and at least top 10 in the 2008 version.
The Schlecks really will have to do something in the coming days, because I'd like to think that they've worked on their time trialling ability, but as far as what they've done this year, no big improvement is evident. Back in 2009, Frank Schleck plummeted from 3rd to 6th, losing well over 2 minutes in a 45km time trial. Right now he has about 2:15 on Contador and 20 seconds on Evans.
Now as far as the big two from previous years go, Andy Schleck and Alberto Contador, Andy made four attacks on the Plateau de Bei (spelling?), but all he gained was two seconds. He isn't gaining enough to time to put away the other riders.
Now for Alberto Contador, he is in the weakest position I think he's ever been in a grand tour: he has at least a minute or two to make up on the Schlecks and, judging by what we saw on Luz Ardiden, he isn't in top form. Bad luck has hit Contador's chances hard this year: he dominated the Giro, which was one of the most difficult GTs in history, so he didn't peak specifically for the tour; he lost a minute in the stage 1 crash, he's had a couple of spills, and his team is nowhere near as good as the Leopard Trek, BMC, or even Europcar team for that matter. He will have to be at his best in the Alps, then gain as much on the time trial, to win. Last year he only gained 31 seconds on Andy, so Contador looks to be in trouble, but he is still the best GT rider in the world.
Lastly, Thomas Voeckler: I would duly love to see the Frenchman win the tour, he is such an amazing character. But I kinda don't like how much he berates his chances of winning the tour ("I have 0% chance of winning the tour"). Well Thomas, a few days ago there was a "0% chance" of you being in yellow over the pyrenees, or at least lose a minute. You lost only about half a minute (at most). That said, the odds don't bode well with his strengths as a rider, but nonetheless it is fabulous to see him do a repeat of his courageous riding seven years ago.