I'm a big fan of FF mirrorless...however, DSLR still play major role in my photography.
DSLR will die ONLY IF mirrorless can track moving subject as DSLR and lenses need to be smaller to go with compact body.
I do look forward to that day
I think this is something that gets overlooked. One of the important capabilities of a DSLR is to perform high framerate shooting with minimum blackout between frames plus the ability to continue to track AF between frames. This is still difficult currently for a mirrorless system to do because the sensor is also acting as the view finder. I have no doubt that over time this issue will be resolved. How long that takes may be academic, because the form factor of higher end cameras is dictated more by ergonomics (coupled with optics). Even if you could remove the mirror, and deliver everything a 1Dx can, most users of that kind of camera would still want the ergonomics that that form factor provides. You only need to consider the number of 5D series users who add vertical grips to improve the ergonomics of their cameras (battery life is a secondary consideration for many users).
With the exception of Leica nobody has really had any success in bringing the sensor very close to the flange. As the incident angle of the light reaching the sensor becomes more oblique, it becomes more and more difficult to capture the light on a digital sensor - hence why Canon tends to "fiddle" with the ISO when you use a f/1.2 lens. That problem will probably dictate flange distance from the focal plane for longer than the presence of a mirror box will.