DP 1.4 was announced publicly in 2016; manufacturers like intel/nvidia still have access to new standards for adoption in new hardware before public announcements. The fact that nv lists 980ti as 1.4 supported just means they did not have certification for 1.4, which the 1080ti does not either. There's not much difference between 1.2 > 1.4. Hardware wise they are the same; DP is just a versatile protocol. There is no hardware limit to the transmission data size, enhancements in packet transmission(software) and other techniques are able to be implemented to older spec. I'm not sure where you got the 9gbit and 18gbit limit as 1.2 is 17~gbit and 1.4 is 32gbit before overhead. As for your HDR question, DP supports many protocols and standards. They are able to passthrough HDR metadata over CTA standards already implemented; this goes back to DP being very flexible.