A entry full frame DSLR would not be a logical move and bad timing.
The 5DMKII has enough pixelcount, but for all else it is actually nothing more than an entry DSLR.
Feature wise the 5D MKII is a very 'old' camera in today's camera landscape except for its pixelcount as said.
Therefore this rumour sounds more like rubish and from someone who can't afford the 5D MKII.
Meaby after the 5D MKIII is released there is room for a small pixelcount full frame camera (which would then be the old 5D rebranded as 6D?) Although even that is not very likely to happen.....
Entry level? Really? Do you even use one? In what ways, apart from autofocus, is the 5d mark ii an entry level dslr? As for putting a 12mp sensor from the 5d into a new body, do you really think canon would market a camera with iso 3200? They'd use the sensor from the 5d mark ii and stretch the technology. Everyone who was going to buy a 5d ii has pretty much bought one. Some will upgrade to a new higher end body, others will buy a second body on the lower end. Still others would upgrade from the rebel, 60d, or 7d. It would be shrewd of canon to puruse this.