Let's examine...
Armstrong:
-Yes age is a factor. Pushing 36 yrs old in tour 2007, armstrong would have lost something. However, he would have gained motivation to train, as he thrives off challenge and people saying that he can't do something. Let's not forget, he was reportedly struggling to find the motivation to train during 2005. A year off would likely give him a huge boost of motivation.
-Still, he would probably be weaker in 2007, even with increased motivation. However look at his competition...
*Basso - probably not racing TDF next year
*Jan - same
*Mancebo - same
*Floyd - An amazing comeback for Floyd would be if he's back on form for 2008. You cannot have the largest joint in your leg cut open, have pieces of it chopped out, and have artificial material inserted in the place of bone, and be able to quickly recover from that. So Floyd is not likely strong for 2007.
*Valverde - Who knows. You can say he's a challenger, but so far he's having trouble reaching the finish line. He's somewhat of an unknown for 2007.
*In 2005, the 5th place finisher was Vino, 11:01 back. Right now he's the best point of reference for a possible Armstrong comeback. Granted, he was doing his lone ranger thing in 2005, and now he has a whole team behind him. Though he is a bit younger than Armstrong, time is not on his side. He'll be nearly 34 at next year's tour.
Then question is, would that gap between Armstrong and his remaining rivals close down a little, or would that gap disapear and take a turn into the negative? Also, does he actually want to race again?
Another couple points:
-No matter what other theories are tossed around for Armstrong's meeting with LeBlanc and the new Prudhomme, the single best explanation would be that he himself wants to ride. Aside from the drug allegations which tour organizers can brush aside by pointing to the Vrijman report (make no mistake, tour organizers care about 1 thing - money. ASO is a private corporation. It's all about image, not personal feelings. Their private beliefs about armstrong, good or bad, has never ever been a factor and it never will be), the other big problem they had with Armstrong was the boredom factor. Now that he stepped aside for a year he's left the door open for other stars to shine in the tour. His return at nearly 36 might might even be a juicy story for them now.
-Several of Lance's big lawsuits that were weighing him down are now done.
-The crowds at the tour were significantly smaller this year because all the really big names were missing. Armstrong brings in the big crowds, even if some of them are there to hope he loses. He would be a very good thing for the tour next year.
Personally I don't think the new signee is armstrong just because I don't think he wants to race bikes again. Maybe a few marathons and a Tri, but that's it. However, there's nothing besides his own feelings that would keep him from returning at this point.
Ullrich:
-I have 2 things to say about Ullrich signing with Discovery...
1) Ullrich > Hincapie as tour leader ;p
2) If he signed, and was allowed to ride in the Vuelta, I could die happy after listening to Tom Danielson throw a hissy when he was replaced as leader for that tour. I. Could. Die. Happy. In fact I would probably die of laughter.