I wouldn't worry. The SGX 540 GPU is plenty powerful, and it should have excellent ICS support, as the GNex also uses the OMAP4 chipset and had the same SGX 540 GPU.
I wouldn't call it an aging GPU considering Google's flagship device uses it.
EDIT: Actually, it should perform pretty much on par with your Droid 3 as far as gaming goes. So you should already have a pretty good idea. A Razr and a Droid 3 run on the same platform, the Razr just adds 200MHz CPU speed and a LTE radio while omitting the keyboard and GSM capabilities.