I'm still using my 1st gen 13" MBP and it's still a great machine... if you need it now, get it now. If you can wait and want to wait, then by all means wait.
The 13" MPB is the killer machine if you can live with the low resolution screen. Because the base price is so low, you can max out the RAM and even add one of more SSD drives for really good performance that you will see.