According to Engineering, this is a low-risk, as R2 is not a radical change in the underpinnings of the OS. There is talk underway about officially certifying SCSP with 2k12 R2, but most of us agree that there should not be an issue. There has been no target build set, as of today.
As far as official support, if you check out the Platform Feature Matrix, Windows 2012 is supported, and it even calls out ALL versions of 2012, so if you do install it, you will be in a supported state.
I have been running SCSP 5.2.9 MP3 on a Win2k12 R2 machine for close to a week without issue. I have applied all the out of the box IPS polciies and the Baseline Detection policy, along with several custom policies.