With regard to people discussing the issue of pixel size versus noise, in modern sensors there are two issues and associated technologies which collaborate to eliminate the problem almost entirely.
Specifically micro lenses and back lit sensor technology. To actually have separate pixels you have to physically separate them with "walls" this was a big issue which impacted noise until the advent of micro lenses. These essentially magnify the incoming light so that none of it is wasted hitting anything but photo sensitive material and bend it around non-photo sensitive material. The second issue is that sensors for whatever reason have all their wiring on top instead of on the bottom at certain points that wiring can block enough light to affect noise, back lit sensors are wired under the photo cells not above, which solves this issue.
In any case though DSLR sensor technology is far from using the most advanced sensor tech possible. In fact DSLRs use some of the least advanced sensors made because they have a lot of light gathering area. Compact cameras use the most advanced sensors because economies of scale and extremely small sensors make it cost effective to do so.
Canon's most light sensitive sensor is found on a compact camera not a DSLR. If Canon used it's most advanced sensor tech in a full frame sensor it would output 210 megapixels, and have identical noise to the D3s, which is still almost a stop better than the 5DII.
So no technically speaking increases in resolution do not correlate with noise.
The problem is though that ECONOMICALLY speaking resolution does correlate with noise. Having advanced sensor technology is expensive and so is having high resolution. Two cameras one with high resolution and one with low noise would probably could be made for less than one camera which has both. That is why there is often a trade off, otherwise the sensor costs way too much to manufacture.
Canon actually used some of the least advanced sensor technology possible in the 5DII so it will be easy to make it leaps and bounds better in noise with increased resolution. At the least you can expect a quarter of a stop improvement in noise. At best you can expect a full stop. Likely it will be a half stop improvement.