TMG 2010 SP1 and UAG 2010 SP1 are supported on Windows 2008 R2 SP1
The news is official. You can upgrade your TMG 2010 Service Pack 1 and UAG 2010 Service Pack 1 machine to Windows Server 2008 R2 SP1.
Check out the details on the TMG Firewall Team blog over at:
DEBRA LITTLEJOHN SHINDER
MVP (Enterprise Security)