I definitely see that happening. With SFX and SFX-L, there's really little reason to keep ATX around anymore. I think mainstream SFF will continue to use SFX as well, but at the more compact end of the spectrum we should see external power bricks and flexATX pick up steam. The former is already pretty common with the big mainstream system integrators (Dell/Alienware etc.), but for the DIY market flex might make a bit more sense.