If this rumor proves to be real we might expect to see a 20 megapixel version of the sensor on the 7D II. If they decide to have the same pixel size on both crop and FF that is.
Would make sense to start off with crop versions to have more time perfecting the internal handing of the greater data flow on the FF models to come. And buy some time. They might even do like with the Canon C100. Incorporate hidden tech that will be used on coming models and open it up with a upgrade later on.