Yes you need to wait for new drivers or use the leaked alpha drivers. I just noticed that on asus drivers site they released a new GPU driver V9.18.13.4801 (2015.05.11 update) give that a try and see if that enabled Gsync
Just be patient. When there will be G-Sync enabled drivers available, NVidia will make sure that we hear about their release. Until then, neither ASUS nor Gamenab can't come up with anything .