So I guess all that's left to be determined is which Astana rider wins it all

Not really--there are still 17 stages, hundreds of miles, and all of the mountains to go, including an epic mountain stage on the second to last day. Anything can happen yet. BUT. But Astana won the Team Time Trial today and now sit second through fifth. Fabian Cancellara is first because he's the world's best time trialist, but he won't be able to keep pace in the mountains. Second is Lance Armstrong, who's won the last seven Tours he's ridden. Third is Alberto Contador, the overwhelming favorite and winner of the last three grand tours he's ridden. Fourth is Andreas Kloden, who has finished second in the Tour twice. Fifth is Levi Leipheimer, who has finished third in the Tour and second in the tour of Spain while riding as Contador's top Lieutenant. Even with some bad luck and form, I can't see all four of them getting overtaken by the competition.

1 Fabian Cancellara (Swi) Team Saxo Bank 10:38:07
2 Lance Armstrong (USA) Astana
3 Alberto Contador Velasco (Spa) Astana 0:00:19
4 Andreas Klöden (Ger) Astana 0:00:23
5 Levi Leipheimer (USA) Astana 0:00:31
6 Bradley Wiggins (GBr) Garmin - Slipstream 0:00:38
7 Haimar Zubeldia Aguirre (Spa) Astana 0:00:51
8 Tony Martin (Ger) Team Columbia - HTC 0:00:52
9 David Zabriskie (USA) Garmin - Slipstream 0:01:06
10 David Millar (GBr) Garmin - Slipstream 0:01:07
11 Sergio Miguel Moreira Paulinho (Por) Astana 0:01:16
12 Christian Vande Velde (USA) Garmin - Slipstream
13 Gustav Erik Larsson (Swe) Team Saxo Bank 0:01:22
14 Maxime Monfort (Bel) Team Columbia - HTC 0:01:29
15 Roman Kreuziger (Cze) Liquigas 0:01:31
16 Michael Rogers (Aus) Team Columbia - HTC 0:01:32
17 George Hincapie (USA) Team Columbia - HTC 0:01:36
18 Yaroslav Popovych (Ukr) Astana
19 Vincenzo Nibali (Ita) Liquigas
20 Andy Schleck (Lux) Team Saxo Bank 0:01:41