Acutally, I simply study all religions a little bit, though I am no expert on any of them. I wouldn't call myself religious at all, since I don't follow any of them. But I certainly would not discredit any prophets without extensively studied their teachings myself. Since you think Mohammed hasn't been discredited yet, why can't there be new prophets coming that won't be discredited either? I mean Mohammed did come after Christ and Moses.
Well. Newton's laws are once regarded as the eventual theory in physics, but when science advanced and new experimental methods become available, quantum mechanics becomes the theory that outdated Newton's laws. F = ma was proved to be only a very good estimation but not fully correct. It doesn't mean we can no longer believe in science. I am simply saying that science updates itself.
I am simply comparing how we practice religion and science, not the actual practice themselves. They both require openmindedness is all I am saying. Fanatism in any practice is evil. Well, except Kotor of course.