For practical purposes, Tuesday will decide the #1 ranking.
Oh, it's possible that the #1 spot could still be in play after Tuesday -- if Roger Federer loses to Robin Soderling. Possible -- but not at all likely. Federer knocked Novak Djokovic out of the hunt for #1 when he beat Stanislas Wawrinka. That leaves only Rafael Nadal. Federer blocks Nadal also if he beats Soderling. But if Federer loses to Soderling, then Nadal can reach #1 by winning the French Open title. And, should Federer go out, what are the odds of anyone stopping Nadal from winning again? The Spaniard is healthy this year, after all.
Nadal is hoping to reach #1, but as of now, he still hasn't clinched #2. That won't be settled until he and Novak Djokovic (presumably) face off in the semifinal. The winner of that, whoever it is, will be #2. If Djokovic doesn't make it to the semifinal, of course, Nadal is #2. If it's Nadal who loses in the quarterfinal, Djokovic still must reach the final to move back to #2.
Andy Murray hasn't quite clinched the #4 ranking, but he's close. Robin Soderling can pass him with a title. Anything else and Murray is #4. Similarly, Nikolay Davydenko is #5 unless Soderling takes the title.
As of now, Andy Roddick is #6 and Juan Martin del Potro #7. But Soderling can pass them both with a final. (Which, to be sure, means that Roddick is guaranteed to gain at least one spot, to #7.)
Soderling of course is #8 and Verdasco #9 in safe points. Verdasco had a chance to pass Soderling; that is gone now. But Youzhny or Berdych could still catch either of them with a title.
Since Berdych and Youzhny can't both win the title, or even make the semifinal, we know that Federer, Nadal, Djokovic, Murray, Davydenko, Roddick, del Potro, Soderling, and Verdasco will be Top Ten next week, in some order. That leaves one spot, currently held by Jo-Wilfried Tsonga -- although word is that the hip muscle he hurt will force him to rest for at least ten days, and perhaps longer; he may miss Wimbledon. So his long-term Top Ten chances don't look good. They're much better in the short term, since he has about a 500 point lead on Youzhny, the next active player. But Youzhny or Berdych can pass him with a final. And since Youzhny and Berdych face each other in the quarterfinal, one of them is sure to reach at least the semifinal, there to face Federer or Soderling. So whereas the bottom half semifinal will presumably determine whether Nadal or Djokovic is #2, the top half semifinal will certainly determine whether the last Top Ten spot goes to Tsonga or to the Youzhny/Berdych winner.
Falling out of the Top Fifteen are Gael Monfils and Fernando Gonzalez; Berdych will take one of the other spots, with Ivan Ljubicic being the main contender for #15, but Nicolas Almagro or Jurgen Melzer could still theoretically nab the spot.
We will see only two changes in the Top Twenty: Almagro and Melzer in, Gonzalez and Stepanek out.
Hitting the Top Thirty is Montanes, replacing Robredo.
The big doubles contest ended very early. The early loss by the Bryans means that they have lost the #1 rankings. Daniel Nestor and Nenad Zimonjic are co-#1. The Bryans are co-#3. Lukas Dlouhy will be #5 unless Kubot/Marach win Roland Garros, in which case Marach is #5. Bhupathi, Knowles, and Paes should also be Top Ten. That leaves two spots, currently held by Marach and Kubot in that order. But Andy Ram or Fyrstenberg/Matkowski could still nab the #9 and #10 spots, or even someone still lower if all breaks just right.