It's not over
It's not over. I know there's a lot of overlap between dottore fans and pantalone fans, but PLEASE know that this doesn't mean it's happening again. His ID is formatted the same as sandrone's was at the beginning of nod krai. Yes, his icon is an NPC 3D render, and he doesn't use the standard playable male model (at least in the face), but keep in mind genshin has been slowly diversifying their models, with the biggest examples being Varka and Alice who have very unique models for playable characters.
And, even if he's not playable, that doesn't necessarily mean he'll die. He's not the type to sacrifice himself, and he's also not the type to go crazy with power like dottore did and become a boss. He's important enough that they foreshadowed him in 6.6, they even hyped him up a bit as "mystery man", using his connection to dottore to reintroduce him to people who may have forgotten him.
As for his popularity, ignoring the fact that his insta reel got over a million views, I don't think it matters that much. Sandrone was one of the least popular harbingers before she appeared in nod krai, often ranking the same or below pantalone, and look at where she's at now that she's gotten to be fleshed out as a character. Pantalone is already starting to gain traction.
PLEASE don't doompost just yet. I mean this out of concern for everyone's happiness, but also out of my genuine belief that it's still way too early to call it.