Another clue comes at the end of the trailer, when Harris and Cruise have this exchange, which is, again, about Cruise, not Maverick. I don't think this is Cruise regretting anything -- probably the opposite -- but I do think he's reflecting.
I have watched the TOP GUN: MAVERICK trailer 20 some times now and I'm convinced this movie is Tom Cruise's own meditation on Tom Cruise's career. bit.ly/2YZ99fn