I have just today reached a milestone and received over 200 reputation in a single day but I'm still receiving up votes today (in excess of the 200 max). I actually got capped at 215 but the up-vote notices are still coming in. What happens to that rep? Will those rep points be awarded tomorrow?
Reputation above the cap just disappears into the void. But you get a shiny new badge for it.
The reason you got 215 is because the 15 points from an accept don't count towards the maximum (same with bounties).
The short answer is that your additional reputation is gone and ain't coming back.
The cap allegedly exists to prevent "gaming" of the system. You can read the justification here and if you want to, you can upset yourself by visiting Data Explorer and checking the "How high would my reputation be if there wasn't a cap?" page;