Parallels 8 Tests OK on 10.8.4 Retina MBP
I just installed 10.8.4 on my Retina MBP and tested my two VMs (one Win7 the other Win8, both 64-bit) and didn't have any problems in windowed, full screen, or coherence modes. Incompatibilities are normally highly configuration-dependent though, so anything can happen. I believe this is primarily a security update so I wouldn't wait too long.