I'm having the same dilema. My Dell is operating well and covers my gaming fix. Its 4 yrs old but I upgraded the AGP vid card a few months ago and it allows me to play games like LOTRO flawlessly. (If anyone is looking for a good AGP card, I think mine is that digitex x1900xt or something) If u really want to know the exact card, send me a private message and i'll 100% verify that for u.
I want to get a MAC because gaming has become less of a priority to me and I love the MAC OS and software (for video, music etc). Its just nicer to use.
I'm in no rush at the moment to buy, even though i want one now ! lol. But i'm gonna wait till after Macworld in January to see what develops. Now, the Aluminum IMAC probably wont be redone, but they may upgrade some components (processor or vid card). I know alot of people upset that the IMAC is pricey for the parts. Honestly, they should upgrade a few of the components.
So a totaly redesign wont happen but by switching to Intel Chips this should make it easier for them to just pop in new parts more quickly then a total redesign.
I'd wait a few months if you can to see what develops. And if you have the $$$$ , the new Pro Notebook will definately get some upgrades sooner than the IMAC. I just don't want to spend a fortune so i'm more interested in the IMAC.
Lets put it more simple: Gaming = PC, Everything else = MAC. Just wait till after MACWORLD before making your decision. You might get some insight into any proposed changes to the IMAC.