My prediction for next seasons heroes
TLDR: I believe the character mentioned at the end of the gallery card and viewed in the picture is a red herring for the new character, and is actually something to do with the lore, the characters will instead be cyclops and devil dinosaur
I have a few reasons for thinking this:
The biggest reason: The way characters were teased before vs now. In earlier seasons the two heroes that were going to come were, not so blatantly, described in the last few sentences of the last card for the season; "and if you play your cards right and they don't drain every last bit of your life force," and "a blathering, foul-mouthed mercenary and a monster hunter as deadly as she is beautiful" are how the gambit/rogue, and deadpool/elsa seasons were teased, pretty obvious. But something changed for the tease when it came to the current season. instead of being mentioned in the text, a hint in the visual was given (the white fox and black cat by deadpool's feet). The end of the card mentioned someone locking down manhatten, which we now know to be kingpin, and no hints were given for black cat or white fox except in the picture, they teased the LORE of the next season with the text. it is for this reason, i think they are changing how they handle character teasers to make it less obvious, and i think instead this character mentioned at the end of the card and is seen, is actually either the villain of the season, or a pawn of them. I personally believe it is a rogue clone made by mister sinister since the designs are similar and hair fits, also explaining why she would have the "exact same thought patterns as [Rogue]."
The character design: obviously the character is meant to be unknown and i think it does a pretty good job of confusing the players just like the daredevil visual did before he came out. Many guess that the character is captain marvel, which makes sense lore wise why she would have similar thought patterns as Rogue. However, the hairstyle, while possible, seems an odd choice and it feels like they're setting this character up as a villain, with the red glow and such that's described. If this is instead a clone of rogue, made by mister sinister (perhaps with the help of emma frost given the stylistic hair) then it would line up with it being purely a lore drop rather than a new character teaser (although if my theory is right, we could get a new rogue legendary skin of the clone)
The bookshelf: taking all this information in, i think it makes sense why not just that character is shown, but also two are teased on the bookshelf, that being a dinosaur plushie and cyclops' glasses. It would be odd if the final teaser of the season was showing off 3 entire characters all at the same time rather than the usual two, and it fits the previous season wherein the characters are teased by visual only, and the text makes no mention of them just as with the current season.
I may be wrong about this of course, and it really could be captain marvel, or maybe even a different version of rogue, but i think my reasoning makes sense as to why it would be a lore teaser rather than a new character teaser, and it would add up why three characters seem like theyre being teased all at once rather than 2 like normal. Unless of course next season is a 3 hero season, in which case ill gladly be incorrect. Of course though, devil dinosaur was also shown at the end of last season as well, except he was a part of deadpool's animal kingdom, however i feel this one is more obvious as the plush is sitting near the very clearly teased cyclops