Im with you on this one, if they used a FF sensor with 45mp giving the same pixel density as the 7D it's a disatster waiting to happen if the resulting IQ suffers anything like the 7D's does.
It will be fine for those who like to brag about mp or use a tripod but for handheld events etc it will be S___e!
Be realistic, if the 7D's sensor was so horrific, then pretty much all of Canon's current APS-C bodies using the same sensor would be dead.
I know, different people have a different noise threshold, but unless you're submitting to the extremely noise-phobic stock agencies or are a terminal pixel peeper, it is really insignificant. Personally up to ISO800 on the 7D the noise is insignificant, and I find it usable to 6400 easily. If you ignore DoF equivalence considerations, then like for like settings with a 45/46MP full frame would have over a stop advantage just from sensor size anyway.
Further bear in mind the 7D sensor is I think getting on for some two and a half years old. Any new sensor should have moved on since then.
There will be many people who don't need a high MP model, or even know what to do with one, but they don't need to get it. In the same way, the 1D X may be a great camera, but it isn't suited for my needs. For those that do know why they want a high MP model, this rumoured X model is spot on. The 5D2 would be in the bin* the second I got one.
*Ok, I wouldn't really bin it, but sticking it on ebay is close enough!