I bet you can still install any OS though. Just select the "Other OS" option. However, this clearly shows that Microsoft is going to do everything in their power to prevent people from knowing of Linux's existence.
However, I actually hope that Linux cannot be installed in the new VPC because I want to be there for all the ridicule and bashing that Microsoft will receive if that happens. I personally don't care. I'm happy with VPC 5.1 and do not intend to install Microsoft program even on my Windows computer.
Remember, since VPC computers are virtual, they now probably contain a Microsoft BIOS.