It depends on what kind of a score you want. If you just want a passing grade, I think you will likely pass it. But if you want to do average or above, you should definetly take an extra couple of weeks of hard core studyin!
Hmmm, the consensus seems that NBME 4 and 2 correlate well. 3 might underestimate, and 1 might overestimate. At least that is my understanding of the matter.