For those who didn't read the article, the game is already released, it's the Paper Mario Thousand Year Door remake.
In the Japanese text of the original gamecube release, Vivian was a trans character. The English localisation of the Gamecube release cut out all references to her being trans.
The article is saying the Switch remake's English translation now contains the cut dialogue that fleshes out Vivians backstory.
In the original Japanese translation, Vivian is referred to as an otokonoko (which also can mean just "boy") and the game often uses otoko (man) and otoutou (little brother) to refer to them - so the intention was most likely to paint them more as a crossdresser.
English localisation completely removed all traces of these, just makin Vivian a girl.
And now the remake, for both languages, makes Vivian explicitly trans.
I feel it's worth noting that everyone calling you he/him or "little brother" or "man" doesn't make you not a girl. She's referred to in game as オトコノコ (otokonoko), which is written ambiguously like that so it can either be 男の子 meaning boy or 男の娘 literally meaning "male daughter". When she's referred to as 'man', she feels insulted, and she uses feminine first-person pronouns and calls herself one of "three sisters."
Saying she's "just a crossdresser" is a possible interpretation, but not one that is clear and unassailable. In translation, she's either just a girl, explicitly trans, or somewhat ambiguous more like the original Japanese, so the people publishing the game don't seem to think of her as just a crossdresser.
All that to say, she's been trans for a while, even explicitly, it's just happening in the English version of the game now.
Birdo is a permanent character in the main roster of characters and Mario 2 is a real Mario game. I will not tolerate all this Bowser propaganda in here.
Even notwithstanding all of the below (several enemies and other aspects of Mario 2 showed up in later Mario games, so we can only suppose its as "real" as any), Yoshi is also a strong contender for being trans. He is consistently referred to as male but cranks out eggs at an assembly-line pace and thus might be biologically female.
But then, so does Birdo. So who the hell knows how dinosaur-things work in Mario's world.
That's great, but, I mean, it's Mario. How are we supposed to know?
I haven't played Mario in a while. It seems like, given the general art style, in order to make it obvious enough to notice, they'd have to flirt with stereotyping.
The Paper Mario games are RPGs, so they're a lot more dialogue-heavy than a normal Mario game. In this instance, the character explains their identity to the player, directly.
revealed that a remake of their 2004 video game Paper Mario: The Thousand-Year Door is slated to revive a character’s transgender identity.
The remake has the character Vivian explicitly discuss her gender identity in dialogue with Mario, stating that after she realized she was a girl and not a boy, her evil siblings started to bully her.