Canon to use the EF mount for mirrorless?

A few new rumors have surfaced lately, both of them seem to be indicating different products. I have a suspicion that Canon's decision on what mount will be used for mirrorless will go down to almost the last day before announcement. This event must rival that of the FD versus EF mount debate that raged inside of Canon back in the 80's.  Canon may decide that the best answer - is to do both.  We are certainly seeing competing suggestions between a new mount and using the existing EF mount.

There is alot of information on the internet, that seems to suggest that Canon cannot build a small camera unless they change the mount. This is really patently false.  The EF mount is currently used from cameras the size of the diminutive SL2 to the large solid magnesium brick called the 1DX Mark II.  If you look at EF based Cameras, Canon's ergnomic larger grips on cameras from the Rebels upwards are much deeper than the mount.  Making it so that no matter what mount is used EF or another one; to provide an ergonomic deep grip, the grip size will dominate any camera. Therefore is nothing stopping canon once they remove the need for a pentaprism or pentamirror from making an EF mirrorless camera that sits at either end of the size spectrum or somewhere in between.

As an example, from the image below we see the range of sizes that Canon has used for APS-C EF cameras. Keep in mind that the only size difference between the various cameras is penta prism (unnecessary for mirrorless), and ergonomic design requirements.  Other than that Canon has the freedom to choose to make a camera of almost any size from the EF mount.

The main disadvantage of using the EF mount comes down to third party lens adaptability (which Canon probably does not care about), and wide angle and ultra wide angle lenses will tend to be larger as the mount is made deeper.

Even still, with an EF mount, this isn't impossible to overcome as Canon has already done something similar to reduce the size of EF lenses for APS-C by making EF-S lenses.  EF-S lenses differ fundamentally from EF lenses by allowing the lens back element to sit back into the EF mount further, essentially creating a smaller depth mount for APS-C cameras using the same EF mount.

For instance, here we have a 24mm EF-S prime.  The back of the lens protrudes further into the camera body than a regular EF mount lens, giving lens designers more freedom to to design lenses.  It's entirely possible that Canon does something similar for full frame EF mirrorless, because once you remove the mirror, you can move the elements back as far as you want until they hit the sensor.

We of course won't know until the cameras are released, but there's certainly room for Canon to do either solution of an EF mount or a new mount and come up with credible products.