Personally I still think that the largest unexploited mirrorless market at the moment is something along the lines of the rumorued Fuji system, rangefinderish body with a selection of small primes.
If Canon do stick to DSLR's then I'd say looking to make some smaller high end bodies might be a good ideal with the Fuji and NEX7 around.
I problem I see with this statement is that, while it may hold in present company, the readers of CR are not a representative sample of the overall camera market. For that reason, I have a question in my mind as to whether the niche for the "range finder form factor with a large(ish) sensor" may be too small.
While pros and enthusiasts can see the virtues of a system that provides a (relatively) high IQ in a small form factor, most people do not understand the qualities of a photograph which make it "good" - and I am not saying that is either right of wrong - it is just that way. Hence, for most users, a phone which doubles as a MP3 player, camera, address book, email client, calendar etc. is perfect. There is nothing wrong with that fact - it just is that way. Hence why Canon et all are seeing so many challenges in the low end of the market, where entry-level P&S cameras are being cannibalised by phones.
I would love to see Canon produce a mirrorless camera in a rangefinder size package, with a selection of small fast primes. I will not be distraught if that remains just a wish. DSLRs are great for my wife's work and for taking on road trips. For myself, I would like a more compact system that I can just throw in my bag when travelling by air, or which I can easily take with when I'm on my bike. I like the form factor of my Zeiss Ikon, but would love something digital in that form factor - but without the weight of a camera that was made before the advent of lightweight alloys! (Oh, and I am not about to drop a whole lot of cash on a M9 unless it can be justified for my wife's work - a 1Dx would be a higher priority.)