Thinking about it, this is truly the best point to end if artist want to move their focus onto other work. As this is the end of major arc. If they still continue, who know which point they could end it as good as this one, considering the spoiler implying this is the best point to end.
Comparing to other Manga that ended the story while LN/WN still continue long after, I feel like this is probably the best case. No Cliffhangers, No "Please if you want to see story really end, read Novel", or such.
If anything, if one day author, and artist want to continue manga in the future, then they could do it as "Sequel". But continuing now would only do harm.