With a new Pokemon Legends Z-A trailer, fans hope to see their favorites in the game. Especially now that several Pokemon that can Mega Evolve have returned for the first time since the Let's Go games, all the way back in Gen VII. However, not every expected creature showed up in the latest trailer.
While no new Mega Evolutions were announced to the disappointment of many, several fan-favorite Pokemon were nowhere to be seen. Just because they haven't been confirmed yet, it doesn't rule them out from appearing in the latest Pokemon game.
5 anticipated Pokemon missing from the Pokemon Legends Z-A trailer
1) Pokemon with pre-existing Mega Evolutions

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Mega Evolution returning in Pokemon Legends Z-A has been a big selling point of the game. However, while some popular Megas like Charizard, Gyarados, and Lucario have been confirmed to return, there are 26 other Pokemon capable of Mega Evolution that have not been confirmed.
Out of the missing Megas, there are the other Kanto starters, all three Hoenn Starters, and Legendaries like both Mewtwo forms, Rayquaza, and Diancie. The absence of Mega Diancie is especially conspicuous considering that not only is it a Generation VI mon but the only Generation VI mon currently known to Mega Evolve.
2) Flygon

Flygon is an extremely popular Pocket Monster from Gen III that has yet to be confirmed for Pokemon Legends Z-A. It would have received a Mega in Gen VI, but the designers couldn't come up with a suitable design for it. This left it as the only Gen III Dragon-type incapable of Mega Evolution.
The absence of Flygon in the latest trailer will dampen its fans' hopes of getting a Mega Evolution this time around.
3) Milotic

Milotic is another fan favorite missing from the latest trailer. It was in a similar situation to Flygon in Gen VI, where the lack of a good enough design left it without the capability to Mega Evolve.
Fans would be disappointed if Milotic, a Pokemon often stated to be one of the most beautiful of all, didn't appear in a game set in Lumiose City, a city inspired by Paris, one of the most beautiful cities in the world.
4) Volcanion

Like Diancie, Volcanion is another mythical from Kalos yet to show up in the promotion of Legends Z-A. Some traits of Volcanion help it stand out, like a unique Fire/Water typing and the only Pokemon with access to the move Steam Eruption, a 110 BP Water-type move with a 30% chance of inflicting a burn.
While there haven't been any announcements so far, fans might have some hope. In the previous game in the series, Pokemon Legends Arceus, all the Mythicals from Gen IV were given special quests where they could be encountered and caught.
5) Xerneas and Yveltal

The fact that the box art Legendaries of Generation VI have not even been hinted at in Pokemon Legends Z-A has left fans confused. In Legends Arceus, both Dialga and Palkia were part of key plot points, while the third box art Legendary of Sinnoh — Giratina — got a postgame boss battle with both its forms.
However, as it appears that the Legendary Pokemon Zygarde is getting a larger story focus this time around, it seems likely that Xerneas and Yveltal end up as part of a postgame plot instead.