Hi cosmopolitan,
Without knowing all of the details (the School/Program, your overall application, if you did an interview and how it went, etc.), there's no way that I can deduce the exact reason why you got wait-listed. I can say that it's highly UNLIKELY that it was because of your GMAT score. A 720/Q49 is an outstanding performance, so trying to improve THIS part of your application doesn't seem necessary.
Most Business Schools tend to be open about their evaluation, when asked - meaning that they'll tell you why they didn't accept you (or in your case, wait-listed you). Have you reached out to the Admissions Department to ask about how your application was evaluated?
Before you make any moves, I'd like to know a couple of things (if you're comfortable giving out the information:
1) What School did you apply to?
2) When did you apply?
3) When was the deadline?
4) When is the NEXT ROUND deadline?
It could very well be that the School is just taking its time to thoroughly review all of the applications, so you might just have to wait a little longer to receive the news.
GMAT assassins aren't born, they're made,
Rich