Megas aren’t returning. Neither are z-moves. Whatmore, dynamaxing and gigantamaxing won’t be a part of the main game, they will however be accessible after beating the main story. No new pokemon will get any new forms.

The region will have more open-world areas, those being:
-The Solaceon path area, including the town itself, the ruins and route 210
-The Iron Islands
-Mt Coronet
-The fighting/survival area

The fighting area gives you the option to battle the Galar gym leaders (original set discluding Piers, the version differences included) together with Leon, Mustard and Peony.

No new evolutions or pre-evolutions will be included for the current forms of pokemon.

There will be, however, several regional variants of pokemon from the three generations before the gen 4 games.
-The Golduck line (fairy/poison)
-The Sudowoodo line (grass)
-Torkoal (ground/psychic) with a new evolution
-The Arcanine line (ice/dragon)
-The Kingler line (poison) with a new evolution (poison/dark)
-Shuckle (electric/steel) with a new evolution
Are in both versions


-The Shiftry line (grass/fighting)
-Mawile (ice) with a new evolution (ice/fighting)
-The Flygon line (ice/flying)
Are in Saturn Diamond

-The Ludicolo line (water/fire)
-Sableye (rock) with a new evolution (rock/water)
-The Milotic line (dragon/flying)
Are in Jupiter Pearl

The underground, while downscaled, will be included. Outside of fossils, plates and evolutionary stones, players will be able to find a new item called simply the “max factor”, basically giving every pokemon of a given species the ability to gigantamax, as if having the gigantamax factor.