Android is a wonderful OS, don't get me wrong. However, there is such a thing as purposeful computing - and that does apply to cameras. Cameras, in particular SLRs are solely focused on taking and processing images. Now, I have wondered aloud here on the forum more than once, that it would be great to have a Depth of Field, etc. tools on the camera to help out. That said, that does not imply that I need access to every tool in the world on the camera - or even available for the camera. Security, why do I want to provide a wonderful path for a possible virus infection of the device - we do not need additional problems.
Now, there is a place for Android, and that is in a support role. Tethered shooting, etc. would certainly be a plus with possibly a remote screen, etc.
But, essentially an all in one device - you have that now with a built in camera. The SLR is designed for a different function and it does not have to have everything including the kitchen sink built into it....