Guh haw, blame Hmurchinson for ruining the thread, not me, he started it! Neener neener neener.

If you could just accept my wisdom, we could all get along better. One of these days I'm gonna run for president of the USA, HA!
OK, on to business.
You see, I started not so pessimistically, I think Apple will update the internals slightly within a revision or two so that 4 HDD's fit in the case, ther room is there, it just needs to be managed a bit better. They should have done it from the outset, but no matter, they WILL adress this issue.
Also, I think a DP middle tier is entirely plausible, and even a DP low end (with less RAM capacity and slower memory and PCI buses.
I think it may be better for Apple to, get ready, you're gonna shit yourselves in a sec, NOT lower prices on the pro towers, 1999-2999, evenly spread, is not a bad range if they pump up the specs a bit, MORE standard RAM, duals, and beefier video cards.
Then, in the place of the PMG4, slot in a
Cube G5 (1299 and 1599) with cube-ish expansion, slightly modified for easier access and internal PS, One optical, one HDD, clearance for a standard 7" AGP slot, CPU daughtercard, and pro level I/O.
The you get a nice spread of headless machines:
Cube G5 1299-1599, both singles
PM G5 1999-2499-2999, single, Dual, Dual.
iMacs have to get under 1399 for the top config, a little overlap wouldn't be a problem. People can choose headless flexibility or AIO simplicity. Put the options out ther and let the market decide. It has worked wonders for the laptop line, and it's the best way to go on desktops aswell.