Nope. More RAM won't help since your graphics are so limited. With your current graphics you would be playing a more modern game at minimum specs (assuming you're playing one that the 750 Ti can handle) and minimum specs for any modern AAA game that the 750 Ti can handle would be having 8GB of RAM.
However, you could improve your RAM situation now for other reasons, and then you would be ready to go when you get your CPU upgrade.
And if you were to upgrade your RAM situation to dual channel, that would improve system performance, and could potentially improve FPS in certain games.
Don't mistake me saying that more RAM would give more FPS, I'm saying that having dual channel, even if it was still 8GB, COULD (not WOULD) improve FPS in...