Okay.. Can someone inform me why full frame-mirrorless would be a good thing? Since I only really care about DSLRs, I don't bother keeping up with the benefits of mirrorless cameras...
DSLR design is mature and beautifully familiar. But as a design which has it's roots in the SLR film bodies from 60 or so years ago, it comes with limitations....like that flapping mirror! So as to ensure a quick take-up of DSLR cameras during the transition time 10-12 years ago, marketing & boardroom decisions were made to make the transition as smooth as practical from SLR film bodies to DSLR, so continuing with the familiar form-factor came to pass. Coming from EOS-1 film bodies to the original EOS 1D & 1Ds delivered a form factor that was instantly familiar and quick to get working with. The new bodies took our existing glass and had major controls in the same places.
Fast forward a dozen years to 2012, a year where we have seen an explosion of mirrorless releases. The digital market penetration has been complete for years now. The market is now ready for new form factors which better suit the realities of digital image capture. Mirrorless is the future. Some of the early releases have been a bit hit and miss, but it's still early days. Expect the mirrorless market to mature very rapidly to a point where the DSLR form factor will be regarded as vintage sooner than you might expect.
I don't necessarily expect a FF pro level M camera to be a great deal smaller than my current 1-Series bodies. Once necessary ergonomic, EVF/hybrid viewfinders, AF speed etc have been satisfactorily delivered, there will be no stopping the M revolution...consigning the lovely old DSLR to history.