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.
1DXII, 5DIV, 5DSR, 8-15/4L, 11-24/4L, 16-35/2.8L III, 24-70/28L II, 70-200/2.8L IS II, 100-400/4.5-5.6L IS II, 200-400/4L IS 1.4x, 17/3.5L TS-E, 24/4L TS-E, 35/1.4L II, 100/2.8L IS Macro, 300/2.8L IS II, 600/4L IS II, Zeiss: 15/2.8, 35/1.4, 55/1.4 Otus, 85/1.4 Otus, Profoto B1