Well, VESA agree that the support that is required for FreeSync to work, will become a norm. So, if you (as company producing them) want to claim that your gfx card/monitor has Display Port 1.2a and higher, then there is the support for FreeSync guaranted.
I think I state it clearly that this is "done deal" and nVidia have to live with it. As for the impact on nVidia G-sync - that is speculative, but look - if something does the same w/o extra cost and as Display Port standard, then how much users pay for some special solution, that lock then into one GFX card vendor on top of that?
Sure few do, but majority will not.
Sales pitch will be - look, we support a new DP 1.2a - it have support for FreeSync!
Sales pitch for G-sync - look, buy this special piece of hardware, so you can have your superb G-sync?
I think is is pretty obvious witch solution will market choose.
As for new monitor, then as long, as you go with the one that have DP 1.2a and higher, you do it right. If you play games a lot and are in need of this function - then I would go for it. Not much games = no need for upgrading the monitor.
Besides, first the 4k monitors prices have to get lower, so… I would not rush things ATM.
On second thought - Netflix already started streaming in 4k quality:
...so maybe sooner or later, there is time to move on?