the limitation here at the moment is with available panels and what can be achieved with
overclocking methods. At the moment, all the available panels in the widescreen format are native 60Hz refresh rate, apart from the 1080p 35" VA panel from AU Optronics which is 144Hz. That could in theory be used at 144Hz for a FreeSync screen without issue, although i can't think of any available or in plan at the moment off the top of my head....
So ignoring that 35" VA panel at the moment, the others being used are 34" LG.Display IPS panels with native 60Hz refresh rate. pairing them with a G-sync module and removing other electronics like the internal scaler etc can allow them to be overclocked up to 100Hz ish, so thats why they are all G-sync screens at the moment. FreeSync doesnt have a separate module and still maintains the scalers etc so cant support any overclocks to that extent. 75hz is available from the Acer XR341CK for instance though with Freesync.
there are some higher refresh rate panels in plan from various places which in the future should mean it's possible to provide 100Hz+ with FreeSync also on screens of that size and aspect ratio.
LG.Display have a 144Hz native version of their 34" ultrawide 1440p panel planned which is probably the most interesting. it's not planned to go in to production until Q1 2017 though. there's also a 1080p version planned a bit sooner in August 2016
http://www.tftcentral.co.uk/news_archive/35.htm#lg.display_144hz
AU Optronics have a 100HZ and 200Hz refresh rate ultrawide VA panel planned, 35" in size with 3440 x 1440. they also have a 30" 1080p ultrawide VA panel planned at 200Hz. like i say, theyve also already got the 144Hz 35" 1080p panel available so it's possible that could be featured sooner.
http://www.tftcentral.co.uk/news_archive/35.htm#auo_panels_june
Some of these panels will require interfaces beyond DisplayPort 1.2 as well, so might be a fair way down the line as graphics cards etc also need to catch up.
