Shigesato Itoi may not be a household name amongst most gamers, but if you say “Earthbound” just about every gamer worth their salt will know what you're talking about. Well, when questioned about whether or not there would be a new Mother game (as it's called in Japan), the creator simply said that it would be “impossible”.
But why would it be impossible? Could it possibly due to all the licensing and copyright minefield issues that the series is known for? Maybe Nintendo doesn't want to publish anymore more games in the series? Perhaps it's that there's a money dispute with the cost of development? If you guessed any of the above as the potential reasons for the game not happening, you're guessing wrong. It's a lot more simple than that.
Kotaku picked up an interview Itoi had with Game Watch Impress, where Itoi-san simply explained that maybe it was time to call it quits...
When I made 3, I thought I could do it, so I did it, [but 4 is] totally impossible.
According to Kotaku Shigesato Itoi is a copywriter and commentator, so he's not beholden to maintaining a creative edge to stay in the gaming business and keep making this highly anticipated sequels.
It's definitely something you wonder about... as a gamer. I mean, you look at BioShock or Call of Duty or Halo or StarCraft, and you think to yourself “How will they top themselves in this next outing?”
As a full-time creative director I can only imagine how burdensome it can be to constantly find ways to keep the fans engaged and the audiences entertained. The Mother or Earthbound series is quite beloved amongst fans, but it's also easy to see how a game like that could quickly fall out of favor with just one sub-par entry. The writing and stories for those games are always the highlight thanks to their quirky characters and outlandish premises.
Of course, maybe they wouldn't be so hard to make if Itoi was making Mother/Earthbound games full time? Assuming that it's something he would want to do and assuming that there's a demand for more of those games. Right now the characters only have been making appearances in the Super Smash Bros titles on the Nintendo handhelds and home consoles, but they don't seem to be on the plate for anything further.
Even still, I think the three games that they've made already are as good as the series will likely get and it's probably best to leave the series with a good taste in the minds of gamers as opposed to stepping over the boundary and creating an overkill moment where people are left saying “Why didn't they just stop at Mother 9? This new cybernetic future warfare premise sucks”.