1.) Phil Schiller has said they wouldn't prevent people from running Windows on intel Macs. However, they probably won't exactly _help_ you installing Windows either. The real question for me is: How soon will we see a good virtual machine software running Windows at high speed under Mac OS X. I hope "Day 1" is the day.
2.) The second part of your question is probably answered in 1.) ... About the chipset, there's only guessing (and a lot of that's been done on macosx.com already), since there's no official info. We'll see as soon as people take apart this devkit machines.
3.) Nothing's stopping Apple from returning to PowerPC. Well: IBM might be, for example. Or FreeScale. Or performance as well as price. But technically... They'll keep a PPC version anyway for the large installed base.
Mac user since 1987. Running Mac OS X 10.8 Mountain Lion on a MacBook Air 11" & an iMac 27" and whatever's newest for my iPhone 4s, iPad 3 and AppleTV 2.
Apple Certified System Administrator 10.6, Apple Sales Professional 2008-2011, Apple Certified Mac Technician.