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Wait a few months

Why not wait a few months to see if Apple releases a 27 inch LED monitor (like their 24 inch one). They usually update their Mac Pro's in January-February and they may release a larger screen at that time.
 
I'll go with the Common suggestion of sticking withe the MBP and getting an external Monitor.

Portability is something that doesn't seem that important untile you don't have it any more. After primary using Laptops for the last 7-8 years, I can't even think of going back to using a Desktop full time.

While the new iMac's are tempting, especially the 27", I cant think of giving up the ability of setting to to work any where I want that I've got with my Macbook.

If money was no object, I'll actually suggest having both the MBP and the 27" iMac. With Apple having included a Mini Displayport IN on the 27" you can actually hook up your Macbook to it and use the iMac's screen as an external screen for it. When you unplug it you a powerful Desktop which you can use for more intensive tasks like Video editing, etc.
 
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