If that reveal E4 members before the game even release, i'm not going to happy about that, it a little too much, even if they have an early role in the game, i would like to see them first by myself, some remake game can show E4 but not a new one for sure.
Even the Gym, we should get around 4-5 Gym Leaders characters reveal before the game come out, the one we'll know before the game out are the evil team members, it would be cool if they won't spoil the leader of the gang and show only grunt members or some big rank members but i'm sure they will do it anyway...
Character reveal will go along with new Pokemon since they will use a new Pokemon at least one in the team so unless more new Pokemon reveal, you can't expect more character too see so soon.
And also let me talk about Masters a bit here, while you can say as you want that lootbox/gacha games are gambling but you can't change the fact that this kind of games are doing well as earning money for devs, for a Nintendo game as example, Mario run where you buy a full game once without any more gacha didn't do much, animal crossing pay real money for in-game ticket also didn't do much but Fire Emblem Heroes and Dragalia lost with a gacha for characters earn a lot than first two games, i'm sure i read a report before, Fire Emblem earned 10.7 billion in 2018 and made it to 26 in top 100 most earning mobile game in japan, while the number 1 spot is Monster Stike who earned 130.2 billion following Fate/Grand Order as number 2 spot with 120.4 billion earned and both have gacha for characters.
Pokemon Go was number 7 with 32.1 billion earned by the way, just in case you wonder.