I think the change is already happening - I dipped my toe in the Fuji Kool Aid and found it worked really well. The image quality is comparable with my 5D2. Sure, it's not quite as good in all respects but let's give it a generation or two and then see. If a $1k Fuji is giving a $3k Canon a run for it's money (body plus comparable lens), it starts to sound ominous.
I think the change will come in a couple of waves. First the XXD series will be compromised, then it's the XXXD. At this point, there won't be enough sales to drive development of XD cameras at a reasonable price and they will also vanish. Since it's technically possible, the question might better be phrased "Is the camera-public willing to pay DSLR prices for a high end mirrorless camera?" I think they are.
As other have commented, there are a few things to fix. The obvious ones are build quality and robustness (this could be greatly improved), user interface (this has been improved), battery life (difficult if the camera's to remain compact), focus speed (already solved - see the X100s or OM-D), larger buffers (easy to fix), faster storage (easy but expensive), frame rate (processor dependent but maybe).
If pressed for a timeline, I'd guess the last generation of high end DSLR's will appear around five years from now. This is depressing - I have a small fortune tied up in glass.