Unless ViperPericulosus has access to spoilers that I haven’t seen elsewhere, I’m almost certain that’s either a wish list or wild guesses. In particular, I can’t see Disney and PerBlue adding Della after DuckTales 2017 ended earlier this year, given that all the other DuckTales characters are from the original '80s version.
You don’t think Disney “suggests” characters for PerBlue to add based on what they want to promote? Not all characters, obviously, but some character additions (and one refresh) seem to have been at least partly motivated by promotional concerns.
I’m not saying it’s impossible for Della to be added, just that I think it’s highly unlikely, especially so soon after the series ended. (Which is a shame, because she would be a terrific addition.)
And yes, I am aware that people have tried to list characters from the Owl House, Hocus Pocus, and many more, but I can tell it’s illegitimate by their poor coding skills.