Inversely, say they ended with Bayonetta 3... well, Bayonetta 2 sold about 700,000 copies, INCLUDING both WiiU and Switch. But it'd still be really great.
Say they ended it with Metroid Prime 4... but Metroid Prime 3 was reported to have sold just over a 1 million copies or so. It's no Zelda, so Metroid Prime 4 would ALSO be a massive drop in terms of popularity with fans.
Xenoblade Chronicles 2 sold 1.42 million copies, and many didn't get to play the original because Xenoblade Chronicles initial run was limited to only the Nintendo Online Store and Gamestop, and they completely sold out of their initial run and it didn't get an extensive reprint.
The series may not be Zelda, Pokemon, or Mario-tier, but it's officially a million-selling franchise that's only grown more and more popular with each new installment.