It sounds like it'll be a successor to AMD's adaptive refresh technology, but it's kinda not.
AMD's presentation deck for their FreeSync 2 announcement was first posted by Videocardz earlier this morning, and it's an interesting announcement given what FreeSync 2 actually does.
According to the slides - which doesn't come with an explanation from AMD themselves, but expect to hear more from them at CES in the coming days - FreeSync 2 will focus on reducing the latency associated with rendering HDR content. Developers and manufacturers have been talking up HDR for a little while, but what they don't mention is the extra time it takes for HDR content to render.
By eliminating the display tone mapping from the process - presumably meaning that the tone mapping will be handled by AMD's drivers, rather than the display - it should in theory reduce lag, and improve the experience.
Of course, the kicker will be the amount of monitors that can support FreeSync 2. HDR is going to be a big focus for the monitor market this year, so expect to hear a lot about it at CES.