If you're talking about system ram, as I think you are, then resolution really doesn't have anything to do with it and 4GB is still OK for most things. Might want to consider making the jump to 8GB, though. RAM is pretty cheap.
Yes i meant system ram, cheers guys i thought this was the case, its just that another person commented how i would cripple my system at 1440p without 8gb ram. I wasnt so sure about that though.