I don't have much faith in these statistics, especially since there's a good-spin bad-spin war going on here. I suspect adoption will be strong.
We've got an interesting problem in my office here. We have two IT personnel and one of them is an XP loyalist to an extreme. The other (who happens to not accidently screw up peoples' computers regularly) is very open minded and sees benefits to Vista and runs it himself. Since we have about 20 apps running to do our jobs, XP is having a lot of trouble expanding to meet the load without "chunking it." As a result, we have rolling, semi-annual reimaging of our 160 users' systems. That's ridiculous! I, along with a select few others, moved to Vista last year (understanding that IT won't help us for the time being) and have since had far better productivity and no overall system downtime. There are a few quirks, but nothing as bad as the flat-out crashes and application hang-ups/corruptions we occasionally experience with XP. Having run 7 at home, I'm sold on it. It's even better than Vista because it doesn't have those weird slow-downs (like when you double-click My Computer) and other stuff that is just strange with Vista.
My conclusion is that XP can't expand to meet my company's modern loads as well as Vista was designed to do but the underlying system architecture, while more secure and stable, is slowing some everyday tasks down. However, I can reload apps like Outlook in seconds instead of half a minute like my XP brethren, so overall I'm very pleased and I AM NOT going back to XP because I just don't call IT for anything anymore. As soon as we qualify 7 next year, I'm pretty sure everyone is going to it. Funny thing is, Vista has been qualified in our organization for nearly two years but our branch IT support is split on the matter and we have therefore stuck with XP for the most part.
I think our extreme XP loyalist may feel his job will be gone if we went to Vista. I haven't asked him about 7, but I think corporate politics will override him if he still wants to stick with XP at that point.