The way Mother 3 ended, I still don't really see a chance of a Mother 4.
Mother would be a very interesting release, I can only imagine how many people will get pissed off over the constant "random" encounters unless that was fixed.
Consider it like a Pokemon game where you're in a cave, except that you are always in a cave in Mother/EarthBound Zero.
And the enemies in the game seriously want to shank you even when you have only taken a step or two in the overworld after a previous battle.
But Mother 3 deserves to be translated and released more so than Mother.
I've said this in other places, but I always thought of this as the most ideal way of releasing the whole series:
Translated Mother 1+2, on the 3DS VC since it is a GBA game in Japan, and Mother 3 also translated and on the 3DS.
That's the whole series right there.
Considering we have already a confirmation that GBA games are coming to the Wii U VC, I'm thinking Mother 3 will be one of the launch titles on both America and Japan.