According to string theory, there could be up to like 10 or something. And maybe even beyond that... Doesn't string theory suggest that anything is possible? Big step, science dudes.

and yeah, I think space should replace time as the fourth dimension as that is where spacial dimensions ya know... come into play. Time (As someone here mentioned in another thread) is an illusion, because time exists only because we can't experience everything at once. but then does space only exist because we can't be everywhere at once? I don't know... it's only a theory!