a 4770 would hardly be the "minimum possible" and even a 4670 would be noticeably limited in more cpu limited games. do you not realize just how slow an old 2.0 Opty is? getting a 5830 would be laughable with that cpu. in over 90% of cases his 2.0 Opty will be a limitation on smooth gameplay long before the 4770 will be. I can understand maybe getting a 5750 or 5770 even though they will be severely held back but suggesting a 5830 just doesnt makes any sense. I will never subscribe to the idea of buying a card that you cant come remotely close to actually utilizing just to use AA. 15-20fps is no better with AA than without it.
I think you are overestimating the changes in a year. Granted cash is always the best thing to have, but you also lose money if you need to sell or dump equipment later. That is why the RAM is a bad investment since there will be minimal improvement but it will definitely go in a year. A 4770 likewise will have no place in an i7 build so he'd have to sell the card for whatever he can by then. I doubt he'd get much by then since the 4770 is already at the border with current games (close to 30 and under it in games like far cry 2).
That is why I advocate he get the best bang for the buck with DX11 card even if he is CPU limited now. A card llike that will retain higher resale value should he want to change entirely in a year, but could also be saved for the i7 build and last for quite a while as well. Crossfire is also an option for high end performance for cheap if the cards do drop in price.
Even if new cards come out by that time they will likely be $300+. In the $150-230 range, I think we'd see at most a one model shift so 5850s may be around the high end here though hard to come by as these cards start getting EOLed.
I don't know if 5830s will be in the 150-230 price range or if the performance is closer to the 5850 or to the 5770. Reviews and pricing aren't out yet, but if it performs like a 5850 but fits into this price segment I'd say it's the best value for the money. In a year from now it would have at least midrange or higher performance (I imagine 5770 will be low end by then) and you could get a second one to get high end performance (or sell it).
Of course best bang for the buck depends mainly on price so if you can pick up a 4770 for under $50 than by all means go for it. Otherwise I imagine you'd see about a $50 loss from selling either the 5770 or 5830 in a year (assuming once again the 5830 is in the low 200s).