I imagine tricking the Boot Camp Assistant will still work
If you wanted Windows XP on Boot Camp you ran the assistant, unticked everything apart from 'Install Windows 7', continued put the Windows 7 install DVD in, when it rebooted you held Alt until the startup screen appears, swapped the DVD for a Windows XP one, and continued booting. You got an XP install unsupported by Apple which still worked in Boot Camp.
So I imagine that you will be able to do the same with a Windows 8 install DVD and a Windows 7 one, except for perhaps on the very latest machines which may have an EFI which doesn't support Windows 7.
Biting the hand that feeds IT
