Update: I mean the update to the MBP model, as you can see in the Buyer's Guide.
But someday (this month or next), 2.66 models will occur in the refurb section of the Apple Online Store for 1999$, so you will never be on the safe side.
Just buy the 2.53 model if you need it now, if not, wait for a better deal/model until you can't wait anymore.