Olympus of course in reality decided that digital cameras would one day be far smaller than 35mm cameras. Ironic then that the OMD EM5 is not that much smaller than an OM10 35mm film camera. However, Olympus and originally the others in the FourThirds Group were right that one day that there would be enough megapixels and improved signal to noise in theory, that would allow us to come to where we are today With the mFT format- and this is likely to be pushed to 20mpx at some point.
The limiting factor was optics, but in reality many full frame lenses are best stopped Down to mid f2 to f3.5 so at that the Depth of Field is about the same as the sub f.1.9 prime lenses.
However throwing reality aside in the Wake of Nikon's wonderful Df-g full frame, why don't Olympus look at going a step further at a lower price tag: putting a 36x14mm sensor in an old OM body- no autofocus, full compatibility to OM lenses and Conversion rings to other FF Legacy gear.
Autofocus is what takes up so much of the processor Power and necessitates more room for Electronics. However you could have some low intensity CF or on chip based PDAF focus assistance such as live view focus "peaking" and Depth of Field preview. You could add an in-body infrared IDM laser shooting from the prism. Or sod it and just rely on ground glass and the split objective Mirror Method ( which some Companies will etch retrospectively to reflex Mirrors on DSLRs by the way. )
Even a last generation Sony 36mm sensor at under 16 mpx would Catch the imagination and bring many an OM hoarder of lenses out the closet.
The OM series With the OM10 became the market leading pro-sumer camera range for a while in the 80s before the evil empire of plastic and EOS came to the world. In effect Olympus built very good 1970s cameras until the late 80s and could not make the transfer to autofocus, which always seemed to me to be a bit of a removal of the Whole feel of photography. Back then I reckon they should have kept top end of manual focus, With better in camera exposure Programming, and not tried the OEM camera system they did. They could have developed AF in their own time, awaiting patents to run out and so on, or pioneered full frame, manual focus cameras.
Olympus has made a great direction and now has Three legs to stand on: mid to high end consumer compacts, the mFT compacts and the prosumer OMD EM series. They showed that they could flog an old horse With the 12mpx sensor for Three crucial years, re-establishing the brand on an sensor made for the last white hope of FT DSLR. So they will no doubt have a good run With minor tweaks to the OMD system line up, and hand me Downs to mFT compacts and maybe lower Down as I expect into single lens non system mFT.
But if only, if only they would dare to do an D-OM full frame!