That's right, a racing title, apparently a mix of Diddy Kong Racing on the N64 and F-Zero.
When Metroid Prime 4 was announced past year at E3, the conclusion most came to was that Retro Studios was working on it.
It makes sense that Retro, which has been quiet since the release of Donkey Kong Country: Tropical Freeze on Wii U, would have something in the works that's ready to be shown at E3.
On a personal level, if this is Retro Studios next game, I'll be hoping they're working on something else. The game is tipped to be more akin toF-Zero than a traditional Star Fox title, hence the "Grand Prix" portion of the game's name. But, naysayers aside, the suggestion of a new adventure for Star Fox could be true, and not just any old game. Here's hoping that Nintendo Australia don't rename it "Lylat Wars: Starwing Grand Prix".
"It is actually a racing game".
Information from Eurogamer's sources has lined up with what was posted online, but the outlet did not confirm Star Fox Grand Prix as an official title. A sequel, Donkey Kong Racing, was in development for the Gamecube but was eventually canceled due to Microsoft's acquisition of the studio.
The idea of a radical shift of the Star Fox series isn't so bad - the franchise has received its share of experimental titles over the years, and vehicles have already been a staple by the series' own design. However, it's useful to note that Mario + Rabbids Kingdom Battle was widely chastised when it leaked prior to its proper E3 unveiling. And if that's the case, Nintendo is nearly certain to pulled the curtain back on the project at E3 next month.