Don't count on NVidia using Freesync anytime in foreseeable future. The way they see it "we control majority of GPU market share, so they should use our standard, not vice versa".
Btw, interesting enough, they *already* have Adaptive Sync support in their driver - its used for "Gsync-on-laptops". Laptops don't use Gsync module and use standard eDP AdaptiveSync. They use purely artificial restriction to make it work only on "approved G-sync laptops" (translation - ones which paid them $$$ for G-sync "license", which in this case is just the *permission*, not any actual hardware).
And you should see measures they go that *nobody* mods it to work on "unapproved" laptop screens, and, god forbid, external DP, - whitelists everywhere, hardware tamper checks - to the level that its really easy to *brick* your laptop/GPU if you will try to hack it.