Mega Man in SSB4 didn’t prompt Capcom to suddenly make a new title in the series. They just decided to do so later on of their own volition.
Conversely Simon & Richter in SSBU isn’t going to get Konami to suddenly make a new title in the series. Let’s not forget Simon and Dracula appeared in Super Bomberman R and we didn’t see any new game in the Castlevania series later on. If a new title would come out they’ll do so when they feel like it, not because a guest appearance prompted them to.
Also Konami in general doesn’t seem to be doing a lot of their franchises justice these days so I wouldn’t hold my breath.