Actually, this has been an issue even before 2000. It's just that non computer people were not aware of it.
The thing is, as has been stated, so much more systems now depend on the 32 bit architecture than ever before. Desktops are pretty much not the issue as is the infrastructure of our modern computing world.
One of the most important things I've learned progressive technologies won't make it simply because they're better. In the end, it's a business aspect that wins. It's excruciatingly difficult to pull out old artifacts and replace with the new, no so much as a portability problem, but a HUMAN problem.
Besides, mainframes are still in use by the way (especially in banks), no matter how much you think they are obsolete.
By that time, it's 64 bit or bust I guess. But I'm pretty sure the world won't keel over because of it.