I expect a beta trailer that will include some of the worlds that will be in the game, since Nomura said he wanted to add worlds in KH3D that he has wanted in the series for a long time, and since they said they are currently picking worlds I expect we may see a few of the following worlds:
sword in the stone
Jungle Book
Pinocchio
101 Dalmations
Olympus Coliseum
I expect to see atleast 1 maybe 2 of these worlds, Olympus Coliseum for sure.
Besides that I think we may get some battle footage, and if possible some voiced scenes though I doubt it, unless they have already started voice recording.