I think what a lot of people (including myself) would like to see is a Mac Pro that's run through a photocopier at 50% reduction... a desktop machine (I won't say "PC", even though it would be a personal computer) that is actually expandable on the inside... room for up to 3 hard drives, a few PCI slots (and a PCIExpress slot), etc. Cube size, or slightly larger, with an aluminum or magnesium case would be ideal.
The problem with the Mac mini (and I have two of them, so I'm allowed to say this) is that you can't expand it. Yes, you can up the RAM, and you can even swap out for a slightly larger HD... but you can't put in a full size HD, and you can't add a second video card, and you can't add a second optical drive... and I don't want to hang a lot of third-party add-ons off the side of the machine.
The ONLY Apple machine now that allows for real expansion is the Mac Pro... and it's just plain overkill for a lot of casual computer users.