This would require accurate forecasting from Wave's hiring manager, but irregardless, the cost of hiring a few people early or late won't affect overall burn much, Wave simply extends payment out for any expenses they have for a month until some more checks clear. No biggie.
I can't see any "huge" opportunities arising that require Wave to desperately expand before revenues. If this is the case, I'd be surprised considering the slow rampup of the technology and acceptance.