I don't think there is any reason to believe that there is a limit to how "much" the Universe can expand...
I guess it can keep expanding for ever, so there is no "edge" that if the Universe expands beyond it, something will happen.
What would be, past that point before the Universe has managed to expand there yet?
I think that the most honest answer is, nobody knows.
But if our Universe is infinite in all directions, then it is, just an infinite Universe which is expanding... So the answer is... More of the same stuff more or less.
But all that is far beyond my understanding so I could be wrong.
- Also I think you need to format your question better:
If the universe is constantly expanding - that could mean, that there is a point (after which) the univese hasn't expanded past yet. With that in mind my question is: What could there "be" past that point?
Which is a very broad question involving much speculation and probably bellongs in meta