Ahh silly people still worrying about 64-bit programs.
Anyway, you have to wonder why they still haven't gone 64-bit for this release. I'd like to think they'd still want a chunk of people who are running Tiger and Leopard to have compatibility. Same goes for Final Cut Studio. If they released a 64-bit version as of right now, there wouldn't be compatibility for either. I'm sure people don't think about stuff like this, so I'm throwing it out there.
Yes, I agree that people SHOULD upgrade to the latest and the greatest, but that's not how it works. People upgrade when they can, and it's always over a course of time. I assume in another couple of years, most software WILL be 64-bit. And yes, iTunes X should finally be 64-bit when it's released. Snow Leopard is step one for Apple to gear everyone up for 64-bit.