Do wait
Chances are the new MBP will be a significant upgrade, not, as with the last several iterations, more a spec bump.
As they should be released soon, by most every criteria it would be advisable to delay a purchase until then. Unless one wishes a new MBP with an internal optical drive (which the new models will probably no longer have), and even then one should wait, as the current models will cost less once new models are released.
If needing the computer now, it would surely be advisable to purchase something used. Buying that new today, and selling it on in a few months time, includes a decided price penalty for that privilege. A used MBP, particularly those refurbished by Apple, will be perfectly serviceable, and someone else will have paid the price of walking it off the new car lot.
In reading some of the related threads on this forum, you are sure to learn of the anticipated advantages of the upcoming MBPs, including: Ivy Bridge processors, more speed, likely better GPU, the advantages derived from no optical drive, and not least a good chance for a stylish new case redesign, more like the current MacBook Air. Screen resolution may also increase, as well as other looked for improvements.
Why would one want to pass on that? And, if so, then in not opting for sound savings with that used, but otherwise just fine?