There are hidden files in the Mountain Lion version of Boot Camp that seems to confirm the next generation of the Mac Pro and the iMac. In a Boot Camp configuration file, there is information that tells the software what models of Mac can boot Windows from a USB-drive.
The file includes the mention of the existing Mac Mini and MacBook Air, but is also mentions iMac 13,0 and MacPro 6,0 models, which do not exist yet. This makes sense because the current iMacs have not been updated in almost 500 days.
An Apple spokesperson also said that the Mac Pro is expected to be delivered sometime in 2013.