Their fear is very valid
The same applies to meseta pso2 collaborations like the Final Fantasy XIV collaboration with Odin (which exists as far as I know) where I do not understand how much Square Enix is involved that for Sega to be able to update assets there. When it was purely just Phantasy Star-related items (such as character outfits, cameos from different games, or other Sega-related possessions ) I could imagine that this likely would have been done, or at least would be done. But in the worldwide variant we don’t have the presence of Cougar NX therefore I don’t exactly know if there are other complications regarding Sega’s properties that may also contribute to not updating everything they can within reason.
I can imagine that likely out there we will still see somebody wearing those old collaboration things even when they are not awakened to the same standards as new makeup in a similar manner and that there definitely would have been outrage if it was made obsolete or unusable. Collabs who have experienced their makeup removed nevertheless have their assets exist on the sport so those will likely still be accessible for jp players.
Only improvements we will likely see is the brand new engine enhancing shadows, shadows, colors, particle effects and projecting them from the drapes. You may have a look how just implementing better shadows and colors can enhance old equipment by assessing ReShade screenshots. Collabs that have experienced their cosmetics removed still have their resources exist on the game so those will probably still be available for jp players. Only improvements we’ll likely see is the new engine enhancing shadows, reflections, colors, particle effects and projecting them from the outfits. You may have a look how just applying better shadows and cheap Phantasy Star Online 2 Meseta colours can improve older equipment by assessing ReShade screenshots.