"This won’t mean that older programs won’t run, but that virtualisation will be used to make them run. The key drivers for this are performance improvements, but also in an attempt to sidestep regulatory programs." - from article
Don't know what that means, but from what the rest of the article says, it's supposed to make things faster.
Also, according to the article postd by spatula, it looks like they're dropping programs like paint, and movie maker from the os installation, but you will still be able to download them from the microsoft website for free if you want them.
I'll keep xp as long as possible, but windows 7 looks like it's going to be a huge improvement over vista, more like xp but with even less in the initial install, which will make it run faster, but we'll see.