So you're concluding, what, that if you buy a subsidized iPhone now and want to upgrade in six months when it includes 32 gigs ... or if there's some super iPhone Plus tablet in a few months ... then you're screwed and have to pay more? My experience with AT&T Wireless/Cingular/AT&T is that they talk a tough game about upgrades, but nearly always end up letting you buy a subsidized phone if you start a new 2 year contract fresh.
That's what the letter of their policy says, yeah. I've never personally tried to get two subsidized phones within a two year period though, so I'll defer to your personal experience.