The Mac Rumors never stop, even when there's nothing to monger about... especially in regards to new Holiday iMacs:
While details remain scarce on what specific updates will be forthcoming, it is fairly safe to assume that no major design changes will be introduced, since the aluminum iMac has provided the template for the new look of the MacBook, MacBook Pro, and 24-inch Cinema display. Some sources, though not reliable, are suggesting a new 30-inch form factor that would retain the black-framed look.
More likely, however, are internal upgrades for the existing 20 and 24-inch models, including processor bumps in keeping with the updated Montevina-based chips currently shipping in new MacBooks. Another likely change is the move to better, Nvidia-branded graphics cards in all models, replacing the ATI Radeon 2400 and 2600 HD cards currently in use. Nvidia has clearly become a supplier of choice for Apple, and their presence in all Apple notebooks provides strong evidence that we’ll see them in Apple’s desktops, as well.
Mini DisplayPort, the royalty-free new video connector present on all new Apple notebooks will likely also make the jump to the desktop in new iMacs.
The big question, of course, is not whether Apple will update iMacs. Natch. But what about Mac Minis? It's increasingly looking like that whole product line is being put out to pasture.
New iMacs Before The Holidays? [The Apple Blog]
