This is difficult. The methodology of science obliges us to stick to known mechanisms, unless the *need* for some new thinking is *demonstrated*. It is going to be practically impossible to demonstrate that prophetic dreams actually do happen, given the complexities of the impact of dream experiences (and false memory syndrome generally) on waking consciousness.
That is not quite the same as saying that precognitive dreams never happen, of course. But it is to say there is no practical need to imagine that they do in fact happen, which is very nearly -- but not quite -- the same thing.
There are other ways of attempting to demonstrate pre-cognitive powers or effects, however. Some of these are deeply thought provoking. Should any such effect be demonstrated, I think that science will eventually catch up with experimentation by revising its ideas on the relationship between time and consciousness.
Some scientists seem to be groping towards the idea that time is created by minds "choosing" the future. If mind really is fundamental to the structure of the universe and is somehow involved in the creation of new moments of the present, then precognition would not seem to be quite so impossible as it does presently.
