Guild Wars 2 will be able to run on older machines with no issues. From what I have heard, the computers that they play the demos on have outdated graphics cards. It's what I heard, so I am not 100% how accurate that information is. Also, I believe I read somewhere that if you can run Guild Wars, you should have no problems running Guild Wars 2.
Supposedly, Anet are designing the game to run on older hardware. Also [as mentioned already] TOR has a poorly optimized engine. So I personally wouldn't really use TOR as a yardstick of great technical performance.*
I suspect at worse you;ll be able to run at low settings in GW2 with suc ha setup. Although constant hardware upgrades are part of the PC gaming cycle so we can only expect so much. Not every MMO is made to run on a calculator ala Warcraft.
*I have no issues or bugs in TOR. But it's clearly not optimized to the degree as mass market World of Warcraft. Not slamming TOR.