Miners make coins, After they are done 'making' them they dont eat them now do they ? lol
They'd probably USE the coins & buy stuff or trade with them in Mt GOX or some other place.
Becoming merchants & users themselves.
If more people mine, that does not mean that more coins will be created.
The system is pre-programmed to output 144 blocks every day.
No more - No less - Regardless of the number of miners in the world.