IGN at E3, Miyamoto said there's "only so much capacity" within Nintendo's internal staff, where the next hypothetical entry would likely be developed.
"I certainly understand that people want a new F-Zero game," Miyamoto told IGN. "I think where I struggle is that I don't really have a good idea for what's new that we could bring to F-Zero that would really turn it into a great game again. Certainly I can see how people looking at Mario Kart 8 could see, through the anti-gravity, a connection to F-Zero. But I don't know, at this point, what direction we could go in with a new F-Zero."
Miyamoto added that, while Nintendo brought other developers to properties like Star Fox and F-Zero previously, the company would prefer to develop those series "internally" from now on. He also noted he's been trying to increase the company's internal staff to allow for more ongoing projects at any time.
F-Zero Climax, released only in Japan in 2004, represents the last F-Zero game, but it's approaching ten years since the series' last major entry: F-Zero GX on the GameCube. Going by Miyamoto's comments, the best that can be hoped for now is Captain Falcon's return in the upcoming Super Smash Bros. - and even that, like the Cap, is up in the air.