Shadowblade brought up an interesting point on his 70-200 thread, which I felt deserved to be a whole new topic unto itself. He said,
Not the E-mount - that's a mirrorless mount that will stay around. Same with the Canon EF-M mount (18mm flange distance and 47mm throat diameter). Both are suitable for full-frame mirrorless lenses.
EF-S will almost certainly die. So will A-mount. EF and F mounts also have uncertain futures, as they will have no reason to exist once the mirror box is supplanted. The mount itself may survive, since their larger throat diameter is even better for developing lenses (particularly tilt-shifts and lenses with wide apertures) but they may no longer use the same flange distance (e.g. the sensor may be moved 18mm behind the mount instead of 44mm), rendering current lenses unusable on them.
Interesting subject.
To me, this is an important consideration in future lens investment questions, because I agree that modern camera mounts
do have a questionable future, and I further agree mirrorless will eventually replace DSLRs (the same as DSLRs eventually replaced film).
Canon has proven they have no problems scrapping an entire lens line, to make room for a new mount system, leaving the owners with a suddenly-worthless lens investment. By contrast, Nikon showed consideration for the owners of its past lenses by transferring the F-Mount to the modern DSLR age, which enabled Nikonians to still make use of their lens investments on their new DSLRs.
But the question is,
would Nikon do that again, especially with some of the limitations the F-mount has, now exacerbated by having to adapt to mirrorless? It's hard to say.
I can't imagine Nikon scrapping all of its modern lenses, that it's in the process of upgrading right now, and I also think the same limitations don't apply here either. (Canon's FD lenses had no AF.)
That said, I believe it is highly-likely Nikon is eventually going to announce a mount switch, when mirrorless becomes the standard (and I have no doubt it will, probably in less than 2 years).
However, I do not believe that either Canon's or Nikon's lens portfolio will become instantly "obsolete," as Canon's FD mount did. Why? Because of
adapters. The ubiquity of adapters (and the fact Canon/Nikon lenses are already AF) will enable those with a considerable investment in high-end glass to continue using their lenses, even if Ca/Nikon changes (or, likely, modifies) its EF and F-Mounts. In fact, even Canon's elder F-mounts can now be used on Sony mirrorless cameras, because of adapters, which has markedly increased the value of elder FD glass.
Manufacturers would also offer a "remounting" service as well. Does anyone else see this as being an issue: The future of DSLR lens mounts?