I've just got information for Pokémon Legends: Z-A; regarding the next trailer explaning the game in-depth. There's no precise release date, this information will be revealed at May 2024 (no day confirmed though). The graphics are very pleasant and the game runs smoothly, unlike the last Nintendo Switch mainline entries. They might have been able to do this because of how segmented are the in-game areas.
You yourself will be a private investigator working for the Looker Bureau, now run by Emma and Mimi the Meowstic. The protagonists are not Calem and Serena, but they resemble them a little bit, the official names as of right now are unknown. As you keep completing your Pokédex, you will be able to use it to solve your assigned cases. The trailer shows how Pikachu's dex entry information is used in order to track its footprints. They thankfully have relaxed a little bit with the Pokédex tasks, as now it takes less to perfect a Pokédex entry (based on what it is seen). The starters are Snivy, Litten and Piplup, no information about if they will have regional forms or special megaevolutions.
The game is set in Lumiose City and its surroundings (don't expect to go too far away though). Instead of visiting separate world areas like Pokémon Legends: Arceus, you'll get to time travel between the different epoques of the city with a special machine that does not only time travel yourself but your entire base of operations (the Looker Bureau). It is said that this machine is powered by a very unique Pokémon, but details are not given in regards to this. You will start at the present (ten years after Pokémon XY) and you will be unlocking both past and future areas, with 7 in total (counting the present as an area).
Battles are shown in action, featuring an oppossing trainer's Mega Charizard X while the player has a Gardevoir that does also megaevolve during the trailer, similar to Let's GO megaevolution.
Gameplay images are not final, according to the trailer.