No, it's not Scotty, and it's clearly not the elder Spock (he has nearly white hair and other clothing and since I'm a totally Spock/Nimoy freak I would spot him everywhere from 3 pixels or a blurr - also it wouldn't fit into the story as known yet)
I'm quite sure it's Sarek - take the Trailer (the one extra with old Spock in it) and go to 1:41 then click pic by pic ... compare "person" who is standing in the background on the right in clothing and slight grey hair and cut with Sarek, who escapes through chaotic rocks with Spock, Amanda and others ...
I have a still and will upload my pic, ... now, there
it's reversed, so Sarek (if he is) would originally stand in the left I assume
dripping wet and totally other body and clothing