Most new games will likely need 3GB's of VRAM to run maxed and maybe more in like a year or so. (some, like Watch dogs and others I can't remember, already need 3GB's)
Now whether or not GTA V will need 3GB's, I don't know, but there is a good change that it will.
You can still probably run it on Ultra, but without some options though.
I feel you, I have the same exact GPU, I should have gotten the 4GB version...