I'd say sell em now because by the time 20nm Maxwell rolls around and prices settle, the best offer you'll get for your 2GB 680's after the massive pain in the ass of dealing with an illiquid market will be a bag of Cheetos. Especially if The Division and Arkham Knight prove to be VRAM intensive and 4K/1440p prices decrease, you'll be peddling paperweights. Problem is, what else can you run in the interim with comparable horsepower and a slower rate of depreciation? Basically nada. If you're prepared to take the FPS hit in favor of textures, a nicely overclocked 290 can bridge the gap and should leave you with more cash to rollover into Maxwell after you flip it. The 780Ti's are coming down a bit and I suspect one will hold its value better than the 680's, but not by much. Regardless, forget SLI or you'll take a bigger beating come resale time. Going with 4GB 770's seem preferable to the Ti depending on the prices and might be the smoothest move for you. Sorry to say it, but the gods of optimal gaming and capital preservation are not feeling very charitable at the moment.