You have to look at what direction Microsoft is going to see 64bit replacing 32bit in the long run. The methods for networking and simply connecting online for the next version of IE if not IE 8 now out in beta form would have to remain the same while the platform would be restructured like mentioned before.
Going from 98 to XP was like going from 98 to Linux in some sense simply the vast difference as far as support not limiting backward compatibility however. You could read Fat as well as install XP on a Fat primary. Don't be surprised if Win 7 doesn't simply throw out the rule book in that sense.