I'm struggling with the same question, so...
I suggest you go for the present Model, if you wait for the next version release you will always be waiting for the next Model.
While I'm not sure which model to get, I'm sure that this is not a valid reasoning: my current model is mid-2009, so given that I keep my laptop for about 4 years or so, I don't want to get a current model only to see a new and improved one coming up shortly afterwards; I'm not the perpetual "wait for the latest-and-greatest model."
Here's what I'm thinking: while faster processor is (almost) always better, an upcoming new and improved processor is not likely to make me wait. Neither will new, fancy power-management features.
What will make me wait?
(1) better ownership experience (ability to upgrade memory/storage in the future), and/or
(2) new fetures that significantly impact graphics and connectivity.
Any input along these lines will be highly appreciated!