All of this can be summed up by saying that it's a question of long-term versus near-term.
In the near term, for high-end users there is nothing better than a DSLR. In the long-term, there very likely will be. When the technology reaches that point, there will be a transition to a mirror-less system, just as there was a transition to digital.
The biggest obstacle to overcome is the viewfinder. Most photographers have no intention of ever giving up the eye-level viewfinder, so to succeed, a mirror-less camera must have a electronic viewfinder that improves upon the optical viewfinders we have today. That's a tall order. The optical viewfinder works at the speed of light, has no electronics and simply reflects light. As such, it's cheap to construct and cheaper still to maintain. (Yes, the original engineering was complex, but after 70 years or more, it's pretty well been perfected).
The tipping point will come when an electronic viewfinder is cheaper to produce and works better. How long that will take is anyone's guess, but I'd be surprised if we see it widely available within the next 3-5 years.
But, I think there is a larger point here that is being overlooked, and that is that for the mass consumer, the digital camera may be dead. I went to the Grand Canyon about three years ago and aside from the enthusiasts with their DSLRs the typical visitor was armed with a point and shoot. I went again this fall, and the majority of former point and shoot users were using smart phones or iPads. (Yes, several people were carrying around their iPads and taking pictures with them).
I frankly don't see and don't know anyone under age 30 who takes pictures with a camera. That's the market that is dead and I doubt if it will ever be revived.