Very soon there will be three major manufacturers shipping full-frame mirrorless system (and perhaps a 4th consortium early next year).
That’s wonderful for competition, but I’m hoping for something above and beyond each vendor duking it out with the others but still locking photographers into their own proprietary lenses: 3rd-party lens designs suitable for all of these platforms.
The flange focal distance of 16mm for Nikon, 18mm for Sony and 20mm for Canon are all so close that a single optical design can assume a flange focal distance of 20mm, and simply be housed in an appropriate lens body for any of those platforms. There has been an existence proof of this approach for years now: Zeiss Touit for Fujifilm X and Sony APS-C mirrorless.
The costs of a single optical design can thus be spread over three (and possibly four or more) competing platforms, making it more attractive than ever for 3rd-party manufacturers.
Specifically, what I hope to see is all-new designs from Zeiss, Sigma, Voigtlander and others. The big sticking point is that Canon and Nikon surely have patented their lens mounts, so what is technically feasible might not be legally feasible, especially if the lens were to support autofocus and full electronic control.
Surely Sigma will find a way (there seems to be some understanding among Nikon/Canon/Sigma), but I give it 50/50 on whether Zeiss pursues the CaNikon market given the legal barriers. But unless Sigma stops designing lenses by the kilogram, I won’t want what Sigma has to offer.