As the iPhone advances, so will games, meaning larger sizes. Especially with a higher display, easily means apps, games and videos will be larger. You need space to carry around alot of games.
True, but again, even if the largest iPhone games jump from the current 100mb to 500mb, that is only a handful, and also how many games are you going to play at one time -- maybe two, three. That's 1.5GB. Most gamers either get bored w/ a game b/c it's too easy or hard or they complete it. Those games get kicked off. Same goes for videos. I think a lot of people just like to fill up their devices b/c they can, not because of any real practicality.
Also, as said, developers are going to develop games that the most # of units can use. They are not going to develop games specifically for a 64GB model because only a small % of iPhone owners would have that model. The development cost to profit return would be tiny. What you are suggesting is a couple generations out.