If you can get by without I'd wait.
In my case I believe Lion will bring resolution independence. This brings up the possibility of a high resolution screen in the Pros. So I see a Pro refresh in the fall as a possibility.
The voice of experience here --->>>. In the spring of 2008 I purchased my new MBP only to see Apple come out with the massive improvement that we see in the unibody machines. It doesn't take a new chipset like Ivy Bridge to introduce new products.
In any event like others have mentioned buy when you need the machine. My old MBP has been a heck of a machine over the years even if it isn't a unibody. Given that Apple is about to release a bunch of new hardware and software, it is best to do nothing until the smoke clears. In that regards I'd wait until August at the minimum.
Originally Posted by zoul-K
Should I buy a macbook pro in august this year? Or is there a newer model about to come out soon? There's speculation about the Air, but not about the Pro i think?
The flip side here is that the AIRs may get revved to the point where you might not need a MBP.