If AMD manages to command marketshare and mindshare for a couple straight years, then maybe we'll see G-Sync open up a bit more, but it's unlikely.
HDMI 2.1 includes a variable refresh protocol (called Game Mode VRR), which AMD says they will support with FreeSync, but it will be voluntary for TV and monitor makers to support it, just like FreeSync. Of course, with Xbone X supporting HDMI 2.1 and FreeSync2, this will help FreeSync cement itself as the "home theater" standard for VRR unless NVIDIA somehow gets G-Sync modules into TVs.
Game Mode VRR
Q: Does this require the new HDMI cable?
A: No
Q: Will this work with 8K@60 or 4K@120Hz?
A: Yes if those features are implemented along with Higher Video Resolution. That will require the new 48G cable
Q: Is this primarily for consoles or will PCs utilize this also?
A: It can be used for both.
Q: Will this result in more gaming PCs connecting to HDMI displays, either monitors or TVs?
A: The intent of the feature is to enable HDMI technology to be used in these applications. Given that HDMI connectivity already has a strong presence in this area, we expect that use of HDMI technology in gaming will continue to grow.