With Monolith Soft and the action game, the LinkedIn profile pointed to it being a Switch game, so it's cross gen at least. There's an outside chance it's a reference to Zelda, but given Zelda was publicly announced at the time this person's LinkedIn profile was updated they wouldn't necessarily need to keep the name of the game they're working on at Monolith Soft a secret. I guess one thing to look out for would be to see if this person turns up in the Tears of the Kingdom credits.
Personally I've felt it's likely Monolith Soft have something non-Zelda and non-Xenoblade in the works, given their size. I know that some people thought that, with the first whisperings of an action game at Monolith Soft stemming from 2017, it's been too long for anything concrete to have come of it; but we can very clearly point to multiple protracted projects on Switch (Metroid Prime 4, Bayonetta 3, Pikmin 4, even Switch Sports). So I'm not sure that so much time passing since that initial hiring call and concept art is any indication of a project being cancelled (though perhaps whatever emerges is very different to the art that was used for the hiring call).