It all depends on what happens with Kingdom Hearts 3. And I think it'll do fine. In fact, I'm willing to bet it'll be the best selling game in the series considering the amount of hype for it (10+ years of it) from everyone. Despite the hype and this franchise in general having lost a bit of steam considering the series went to portable with a bunch of stories with confusing names not ending with 3, even people who haven't played a Kingdom Hearts game in years are going to buy this game. Despite a confusing story for most casuals, the game will still survive on nostalgia alone being a sequel of two games that almost every gamer played or heard of during their childhood being brought back into the next generation combined with new gameplay mechanics and it would be a game every Disney fan would want to own anyway.
So I'm 90% confident in KH3 doing extremely well and Disney wanting this series to continue on after, with or without Nomrua. The only way I see this series not continuing is if this game suffers from bad reception from fans and casuals (which could happen) or it just doesn't do well or meet expectations financially (which I don't see happening, at least in a very significant, damaging number). But if it does well or even better then expectations, if the reviews and general reception is good, then Disney and Square together will, hopefully, expand the franchise more. Which is something I think this series definitely needs... more attention and relevance for the casual and not just surviving on a hardcore fanbase alone. So that hopefully we can get more stories and games and expand the mythology, maybe even beyond Sora's story... which I would still hope will continue being the main story because I feel like we haven't done enough with Sora (despite him being a important plot element in almost every KH game so far) just yet considering that he's still technically 15/16 and could continue being the protagonist for as long as he continue being the same Sora we know lol But I would like other stories focusing on different characters that still connect to the main story while still being it's own separate thing. Kingdom Hearts: Unchained X has that perfect balance we could transfer to other spin-offs, something I think the other spin-offs didn't do well considering it didn't mesh with everyone despite it having its own fans.