Mother 4, no.

Mother 1+2=3 compilation, I sure hope so.

Do fan games count?

People keep saying that Iwata wouldn't have a MOTHER 4 made without Itoi being the one making it... but here's an excerpt from an interview with Iwata and Itoi (Nagata is the interviewer):

ITOI: The feeling of, “I want a MOTHER 4 to be released!” is inside me, too. Even if it’s not something I need to do, I still feel that way. Still, there isn’t someone for me to watch over from afar anymore. If there were a fourth game, I’d want to be the player.

NAGATA: In other words, you wouldn’t mind if someone other than yourself made it?

ITOI: Right. For example, when I watch a good stage play, that’s MOTHER 4. Even if they never intended it to be that way. When I say, “I can’t get enough of this dialog!” you could even say that I, as a “player”, am finishing the world the writer built. Just as everyone finished the MOTHER games for me. So it’d be great if there were such “games” everywhere. They don’t even need to be games, though. If someone wanted to play it in game form, then go right ahead. If someone started making something like “Chimidoro-numa Strikes Back” (translation note: MOTHER 2′s subtitle was Giygas Strikes Back) and you could basically say, “This is clearly MOTHER 4, however you look at it,” who knows, I might just say, “In that case, why don’t you stick a red cap on him and give him a backpack?”

http://earthboundcentral.com/2011/04/shigesato-itoi-discusses-mother-4/

A little later, Iwata says this:

IWATA: …… I don’t believe there will be any new MOTHER games made using the same production system as before.

The wording is pretty clear - Itoi won't be making Mother 4. Not "Mother 4 isn't going to happen because Itoi doesn't want it" - indeed, Itoi would love to play Mother 4. He just doesn't want to be the one who makes it.

Yeah.

Mother 3.

It would be nice. I would love for nintendo develop more ip's outside of the mario/zelda foundation...

Yet he also said that he wants to PLAY another one.