For a while it was looking like the imac was being set up to overtake the tower for some pros and it definitely had the potential. I was hoping that they would release an 8 core and 12 core imac perhaps in the 2011 enclosure, but it looks like the imac is settling into a more comfortable prosumer role.
And that's fine. It might be enough to create a more pronounced market gap between the high end models - a powerful one box solution in the imac, and a supercomputer configurable option in a potential pro line.
Perhaps, now that Apple has just about nailed every possible option for consumers they can turn their attention to their loyal(ish) pro users.
For me, upgradable power, graphics, speed, and memory with intelligent software and connectivity would be great. Let me choose my displays, and I'm in.