MS support finally ends in under two years, so it will be right on time.
Edit: Ninja'd! I hit reply before sswingle's post, I swear!

The next step will be marginalizing 32-bit users, because I have no doubt that Photoshop (a) benefits from lots of address space, (b) can benefit from more registers, and (c) will benefit from wider registers. But making the best of it could very well depend on culling IA32-optimized code.
Adobe says that advances available on newer operating systems and hardware will allow it to leverage the operating system to deliver better performance and focus innovation efforts around areas beneficial to its customers.
That's corporate speak for, "we have a bunch of hacks in Photoshop that were used to make the best of XP and older OSes, that sometimes consume too much of our dev team's time, these days. We would prefer to focus on adding more Windows 7 performance hacks, and to not keep supporting the old ones, thankyouverymuch."