Yeah imo if you have waited this long you might as well try last a little longer for Vega to drop (hopefully soon)
If not, i agree 1x GTX 1070 > 2x RX 480 in most cases simply due to Crossfire/SLI scaling being pretty poor on some games and non-existent in others. But that said....for the price of 2x RX 480 you should be looking at 1x GTX 1080 prices? Either way i understand the FreeSync statement, is a shame G-Sync has a hefty premium but i wouldn't say it's worth the hassle of multi-GPU just for it.