I don't think any open source 3d stack will be able to come even remotely close to the performance of the proprietary drivers, so unless Wayland is thinking of supporting an alternate rendering path not based on KMS and GEM (the KMS symbols are GPL'ed and therefore cannot legally be used by Nvidia/ATI binary drivers no matter how badly they want to use them), there will be no meaningful gaming on Wayland. Maybe the best of the best open source drivers may be able to run a native port of OpenArena to Wayland in 2015. But something with actual fragment shaders? Forget it.
No announcement yet.
Two Features Wayland Will Have That X Doesn't