I believe there's a an entirely new iMac in the works. The current design can't handle the heat Conroe will want to throw at it. And the Kentsfield 4-core processor will want even better cooling. Currently the iMac looks like it has a G5 inside. Apple doesn't like their Macs to look the same over too long a time.
Here's the Conroe processors I hope Apple will use in the all new iMac:
Core 2 Duo E6700 - 2.67 GHz (4 MiB L2, 1066 MHz FSB) 20 $1699 & 23" $1999
Core 2 Duo E6600 - 2.40 GHz (4 MiB L2, 1066 MHz FSB) 17" $1299
In January I hope they will offer a Kentsfield 4 core option in the 20 & 23" models - cause they are bigger and can cool Kentsfield much better than in the 17" enclosure - for an additional $500-$800 - pure guessing cause I don't know Kentsfield pricing yet.
Same is true for the MacBook Pro. It needs to go Black Anodized Aluminum with an easy HD swap out capability like the MacBook which is a radical redesign of the iBook. I think that the new iMac will follow on the heels of the MacBooks intro in September as well. Might even happen in Paris same day as MacBooks - September 12.
I feel so strongly about that MacBook Easy Switch HD feature, that I will not buy a MacBook Pro without it and may resort to the MacBook if they don't put that capability in the Pro model. That's a Pro feature in the MacBook. Makes the MacBook sort of a MacBook Pro Jr. Also note that the next MacBook will have a much better Integrated Graphics chipset that goes with Merom that can handle 3-D very well.