Given PIke's own recent "try-out" on STD, Kirk's appearance next season may just be testing out the casting and writers' concept for Kirk, reintroducing him as a regular at some later point in the series if the audience response is good.
In fact, that's how we got the entire core cast for SNW.
Hell, if Wesley takes over from Mount at the end of season two, I wouldn't mind. I'm ready for more Kirk-Spock adventures.
And honestly Kirk's appearance was a forgone conclusion. I predicted season two at the soonest based on this production team's pattern with introducing Spock.
"Kirk rose very rapidly through the ranks and received his first command (the equivalent of a destroyer-class spaceship) while still quite young." - The Making of Star Trek, Stephen K. Whitfield & Gene Roddenberry, 1968.
It makes sense Kirk would be a captain already. He's already shown to be the youngest at the time. All other captains in TOS seemed far older (Tracey, Decker).
I imagine he gained a battlefield commission to captain during a crisis. After the crisis, it stuck. Much like Lt. Picard taking command of the Stargazer after the captain died.
And I'd rather Kirk have some command experience before taking command of a Starship Class... those seemed prestigious commands in TOS, spoken in awe and reverence.