Jonesy would have a serious case in my books, but we have yet to get a third party that's that young. Even Bayonetta was older when she was added to Smash 4 through DLC, her series being around 6 years old (assuming Bayo was negotiated for in 2015). Fortnite was only over a year old when Smash Ultimate came out, and is currently 2 approaching 3.
I don't expect anybody less than 6 years old for third parties to get in (when it comes to series). Joker and Hero ver. Eleven the Luminary stretch it for individual characters, but Persona (even without counting Tensei) and DQ are way older than their most recent installments.
It's the real reason I think indies outside of Reimu and Quote are mostly dead, most of them are too new. Shovel Knight, Shantae, and maybe possibly Frisk debatably survive barely.