I was able to gather some information on this years games, and while I do fully trust my source, please do take this with a grain of salt.

-december 2020 release date planned.
-No dlc for these games, as that will be specific to new generation titles.
-this years games are Diamond and Pearl remakes like everyone was expecting. Their names are Forever Diamond and Infinite Pearl.
-The national dex was originally not going to be in the game, but after the swsh backlash, GF decided to make the dlc, to give them time to import the full national dex in these games.
-Pokemon following you returns, and it's going to be a feature for all future remakes, and let's go games if GF decides to continue that story.
-My source sent me a few pictures of Sinnohian forms, and I could be wrong about this but it looked to me like a Sinnohian Raichu, Scolipede, and Type: Null.
-Dynamax and Gigantamax are the feature, with several Sinnoh Pokemon getting Gigantamax forms, including the starters and legendaries.
-The underground will still function like it did in DP, with bases and mining, but it's also a wild area where you can control the camera, and there are raid dens.
-Catching Dialga and Palkia (they will be in their gmax form) has you in a raid battle, with your rival, your pg counterpart, and Professor Rowan. It works like the Eternatus battle, where you can't fail the catch.
-The postgame will be like Platinum's with the battle frontier and all it's attractions returning. The new areas will still be there of course just like the originals, with the Villa from Platinum, after decorating it, you can invite gym leaders to rematch them.
-There will of course be a postgame episode involving Giratina and Arceus, where you catch them (they have gmax forms as stated previously).
-The mythical events from Platinum (Darkrai, Shaymin, Manaphy, and Phione) will be available in the postgame for everyone.

Screencap this, tomorrow will be the announcement for these games