Sooner or later more than 3GB minimum RAM will become normal also for better optimised big 64bit-only games that aren't constrained by the limits of 32bit versions. But well optimised games will have more reasonable minimum requirements for CPU and GPU. Cheap RAM and vast address space mean that some space optimisations are things of the past, at least in those case in which using more RAM can increase performances, like, for example, keeping in RAM, once they have been loaded for the first time, as many parts of the game's world as possible, or using RAM for loop unrolling. This doesn't mean that sloppy memory management suddenly becomes acceptable, that's always bad.