Mr M,
I think you're completely wrong to say that the current theory of gravity "doesn't even come close". It actually explains gravity perfectly with the only exception being at the quantum level.
In 50, 100, 2000 years of course our theories will be more advanced, but like I said in my previous post, most of the solid theories we have today will not be completely tossed out for new ones. New, more advanced theories will most likely incorporate large portions of existing theories in them.
And to stay more on topic, the theory of Evolution is one helluva solid theory. You're not going to see it be replaced by anythign radically different. Remember, the theory of Evolution contains proven facts of Evolution: genetic change over time. A new theory that explains the diversity of life would have to contain that fact, so it's not going to be something radically different from Evolution as we know it.