I've never played EarthMother before but i think it's over they always say that they have no plans to make a Mother4.
But it would still be cool to see another Mother game. They could've made one like Starfox Zero that doesn't really have a place on the timeline of the franchise.
Wanna know why Mother/Earthbound was popular?
It's a sitcom in a game.
It's uplifting.
It was American before it was cool.
It's in Smash.
People played Mario & Luigi Superstar Saga
People played PM:TTYD
It's ScrewAttack's mentality in a nutshell.
But I think it's better to have Mother/EB be a fan thing because the law is mean.