I think it can't help but be a recap to some degree, considering you have to go into KH3's plot of Sora using the Power of Waking to save Kairi because she was killed by Xehanort (and perhaps he used the power to do other things related to the final battle, too?) to explain how Sora is in Quadratum in the first place.
So I assume it will show Kairi being broken into pieces (maybe without even showing Xehanort), him restoring her, then him disappearing while sitting on the paopu tree with Kairi before going onto new story elements. Perhaps similar to how he falls "below" Kairi in the KH1 opening, he does the same when it shows him disappearing at the paopu tree--he "falls" down into Quadratum rather than the Dive to the Heart station. I think it would take 30 seconds to summarize that, then perhaps show Riku talking to the star in the Final World before following him and then move on to things related to Yozora / Quadratum's backstory that we probably won't understand until playing the game again (things related to the Gigas and so on).