Prediction:
-iMac 20" 2.0 ghz C2D 9400M replaces the long neglected 17" education model, but is available to the public. DDR2 memory. More or less a iMac version of the white iBook. $999
-iMac 20" 9400M 2.4ghz C2D. $1199.
-iMac 24" 2.66ghz C2Q. $1699. Upgrade to 2.33 and 2.83ghz. Modified Geforce 9400 or Intel P45 platform using mobile chipset with SO-DIMMs for memory but socket 775. Geforce 9600 and 9800S (New SFF model introduced with HP Firebird) via MXM-III socket (as current 24 iMac use). 8GB maximum memory, possibly more easily user upgradable as this is now Apple's "Prosumer model".
30" iMac Pro $2000+? Core i7? Twin hard drives? Possible dual 9800S via SLI? Very unlikely, but stranger things have happened. Who saw the 24" model coming in september of 2006?
A 30" iMac would be an easy purchase IMO.