Not sure if Uprising should get a sequel for sure, but I don't think Mother/Earthbound is in dying need of one. It's a pretty niche series with a unique sense of style & storytelling, which would need aloooot of marketing & possible change to the style of it to sell well. Because yeah, it would need sell well to get approval, company ain't going to make game just because they can, they're a business at the end of the day, and if the company & creator agree it's not worth it, then so be it, for the time at least.
That, and the Mother storyline is pretty much concluded, so might aswell make a new series that take influence from Earthbound, so that the devs wouldn't have to fear the expectation a sequel of Mother would have from the fandom. Plus they can have more freedom to do new cool stuff, so it's win-win for almost everyone