If Canon is going to succeed with a medium format strategy, they will have to deliver Hasselblad quality and close the price gap between MF and top-of-the-line DSLRs. Currently the price jump to Phase One IQ180 and Hasselblad H5D 60 is so big, 5-6x1DX, that only well paid professionals and the filthy rich amateurs can afford it. Canon´s strength is in high quality volume production and, to tempt more professionals and a larger portion of the amateur/enthusiast market, the price premium should not be more than 2.5x1DX.
I will not speculate in how much it takes for a DSLR manufacturer like Canon to build medium format from scratch. But I assume they would make life much easier for themselves by acquiring one of the existing top tier suppliers, like Hasselblad or Phase One.