If gaming at 1080p: A single 770 2GB should do, go ahead and get 2x770GB SLI if you have a 120Hz monitor and want a steady 120 across the board.
If gaming at 2560x1440: perhaps 2x 770 4GB SLI would be best, still debatable (value of 4GB vs 2GB).
If you decide on waiting then good for you, just keep in mind that when the 800 series comes out the amazing 900 series will be just around the corner...