Interstingly, wasn't there a flaw discovered earlier this year that would cause the number of Bitcoins being created with each block to re-start at 50 BTC after all 21 million coins were put into circulation or something?
I think it was expected that it *could* reset after 256 years.
If I understand the problem correctly, the actual behavior is undefined and left up to the hardware to handle. The idea was that 250 years from now, a hardware manufacturer could take advantage of the problem to fork the network or cause other problems.
Regardless, the issue was resolved. If you are still here 250 years from now, you won't have to worry about it.