Not really. Given that the 5D Mark II's sensor is already resolving optical aberrations in L-series
lenses, it doesn't make a huge amount of sense to push sensor resolution significantly higher. Also, many of the recent de-facto body upgrades have seen only marginal/non-existent upgrades to resolution (e.g. 550D/600D or 100D/1100D), and the resolution of some
Canon models has not changed for 4 generations (e.g. G9/G10/G11/G12 - all 10 megapixels). I think any change to resolution on a revised 5D will be minimal, lest even more optical aberrations show up in higher resolution images; the push in image quality is more likely to be in high
ISO performance rather than resolution, and auto-focus (given that the 5D Mark II has the same comparatively awful 9-point AF as the first-generation 5D).