There has been no information given or hinted on what the information is about. The information will be unveiled around 10:00 JST, and if the last few trailers are anything to go by we may see more new Pokemon and new features. I highly doubt Gamefreak or The Pokemon Company will give away much in the way of a storyline since the game is finally getting a brand spanking new formula change.
Pokemon Sun and Pokemon Moon will release on November 18th in the USA and Japan, and November 23rd in EU, and it is a Nintendo 3DS title.