Well, if its a word limit, then they cant really limit the size of the text box to X amount of characters, like they did last year. So unless they do some fancy programming (and judging from the VMCAS site last year, I think that's well beyond them), it won't be limited, since they probably wont have some program dynamically counting the words as you type.
However, I still wouldnt advise going over the limit. Do some editing, and then maybe add that last paragraph. Maybe there's a sentence or two you could cut out?