I have to straddle the fence on this one and agree with a couple of people. First of all, prozac is right. Not much support for gaming with the 64 bit processing. However, if nobody ever bothered to upgrade their computers at all, we'd all still be playing 386 games. So the more of a "user base" we get with 64 bit processors, the more gaming companies will respond with 64 bit games. Read LordBelial's post to see what happens then.....
Strictly talking capacities.........
2^32 = 4,294,967,296bytes, or 4GB
2^64 = 18,446,744,073,709,600,000bytes, or 17,179,869,184GB
So going to the point of absurd, though to make the point, 64 bit processing can realistically address over 17 BILLION GIG of memory! Say goodbye to memory limits for the next 20 years or so fellas.
A 32 bit processor can have an instruction bank of 4,294,967,296 different instructions (1 32-bit word at a time). A 64 bit processor can have an instruction bank of 18,446,744,073,709,600,000 different instructions. In other words, a complex set of instructions in 32 bit machine code might be accomplished by running 1 set of 64 bit code. The possibilities here are geometrically higher. 64 bit code does not represent a doubling of potential, it represents a geometrically higher potential.
So the sooner we can adopt 64 bit computing, the sooner we can reap some of these benefits--such as games made without developers worrying about machine limits.