With them demonstrating 120Hz "HFR" prototypes recently, I'm really hoping that will be a feature on the 2017 models.
Ideally they would support would support a full resolution RGB/4:4:4 120Hz signal via a DisplayPort 1.4 connection. I'm not sure about HDMI, but I don't believe it supports full resolution UHD at 120Hz.
If they are adding 120Hz support, I
really hope they also include support for Adaptive-Sync, as dynamic refresh rate support would mean that the entire range from say 24-120 FPS would be usable, rather than only being able to use divisors of the refresh rate like 24/30/40/60/120 FPS.
Sustaining a constant 120 FPS is a difficult thing to achieve in many newer games even on high-end hardware. But it's definitely possible to stay well above 60 FPS even if you're not able to reach 120 FPS consistently.
It also means that the display could support things like 48 FPS or 96 FPS video if that ever becomes a thing.
Rolling scan is good to reduce motion blur (hence increase motion resolution), but it cuts the lumens down by 50% or more, which is counterproductive to HDR brightness and consequently OLED lifespan (since they will have to increase peak nits even higher to compensate for the nits lost to low-persistence).
One of the problems relating to brightness on OLED displays is their power and thermal regulation.
The current OLED models can reach a peak of almost 800 nits when less than 10% of the display is illuminated at once, but this drops below 300 nits at 50% and only 150 nits with a full white screen.
Scanning the display will only illuminate a small portion of the screen at once - which could easily be set to 10% or less.
A CRT only scans a single line at a time. Ideally the OLED display would let you select how many lines it would hold at once.
So if you have a panel which can reach a peak brightness of 1400 nits, scanning the image becomes less of an issue, since you can drive it at a much higher brightness level than when you are illuminating the whole screen at once.
Now that probably won't let you increase the brightness enough to eliminate the loss of brightness when scanning the image rather than using sample-and-hold, but a 1400 nit display using a rolling scan could bring significant improvements to motion handling for SDR sources which are mastered to be viewed at 100 nits.
Low-persistence is not (or less) necessary if you increase framerate high enough.
Well increasing the framerate/refresh rate is also reducing persistence, it's just another way to achieve that.
The problem is that you need to reach around 1000 FPS at 1000Hz to match an average-performing CRT display.
You would need something like 10,000 FPS with a 10kHz refresh rate to have
really good motion handling when you consider that these displays have a much higher static resolution than CRTs.
It's far easier to reduce persistence through other means than increasing the framerate/refresh rate.
A combination of the two is a good compromise in my opinion; interpolating to say 120Hz while also using a rolling scan or strobing the image - though that technique is only suitable for video, and is an imperfect solution.