To optimize stereoscopic rendering to be as fast as normal mono rendering (or even faster if stereo is half size in top-bottom & left-right modes) we could render only single eye per frame. Left eye for odd frames and right for even frames. Only rendered view would be cleared, another one would continue showing previous frame.
This would reduce animating frame rate to half e.g. 30 with 60Hz screen. Biggest question is how disturbing would it be when left & right eye frames update separately? How would it look in 3D screens? If frames would be blended with half alpha (like using temporalAA) would it add motion blur and look nicer?