IMO 2gb on Vram should be enough for a couple of years @ 1920x1080p, and at 1280x1080p it will be even less demanding. i have a 2gb 770M in my laptop and i have no issues running games right now. Laptop hardware never performs as well as desktop hardware.
You may have to turn down AA of future titles, but there is no way for anyone to know for sure how demanding future titles are going to be. Don’t let people talking about Watch Dogs get you worried, the game is poorly optimized and they are working on a patch to correct the issue. Look at BF4 it uses 1.8gb of Ram, though it is not the most demanding game out it just gives you an idea. MLL is a killer on GPU’s and the 770 gets 52 fps on very high
Here you can see how the 770 performs...