May I say MacsAttacks really knows their stuff! I'm in two minds as to whether I wan't those upgrades to come through at MWSF as it would mean I would have to cancel my imac that's on its way now... Also the system is powerful enough to handle anything I'd want to throw at it, Pro tools LE, HD video and maybe a sneaky bit of HL2... Does this mean that a similarily configured MBP and Imac would perform the same?
Santa Roas - the mobile chipset - is slated for a March releae... Which by my guess puts it in an April/May timeframe for updates to the iMac, MacBook, and MacBook Pro to start to appear...
...if Apple do not do something unexpected and completely redesign the iMac or iintroduce a completly line with a new form factor that would allow them to use desktop components.
My instinct is that they will just wait. We will get Leopard about April, and then upgrades to the iMac and MacBook in their current form. The MacBook Pro could use a ground-up redesign. Now that the Intel transition has been completed (using the same old form factor for the most part), i can see Apple wanting to phase in a new look over the next year.
On the question of memory... I have a MacBook with 1GB, and a Mac Pro with 4GB. Except when doing some "heavy lifting" I don't see that much difference in performance. Looking at the memory usage on the Pro, I think 2GB would be fine. The only time more really makes that much difference is when running Parallels. Now there is an application that loves more memory.
I would expect an iMac to come out slighty ahead of a MacBook Pro - mostly because of the stock Hard Disk in and iMac. For general usage I doubt you would notice the differnce.