The latest edition of the Official Nintendo magazine contains an article titled 'The Brief History of Retro Studios'. While there was no official confirmation that a Starfox Wii U is in development by them, the magazine may have hinted at it being a possibility with:
"“While some suggest this new project is likely to be a return to the Metroid franchise, we’d love to see another Nintendo hero get the retro stamp of excellence. After all, having rolled out the barrels for Donkey Kong, perhaps it’s time Retro pulled off a barrel roll of a different kind.”"
Being the official magazine of Nintendo, this begs to question, do they know something we don't? We sure hope so!Source