A Banjo-Threeie isn't out of the realm of possibility. 20 years ago Banjo-Kazooie was released. 10 years ago Nuts & Bolts *shivers* was released. Though, announced this year would mean a couple years from now, already breaking that trend. No rumors, that I know of, and Rare specified on their anniversary that they have no announcement at that time, other than 20th anniversary merch (using their glorious N64 designs) and a **** all interview with Gregg that was more an ad for Sea of Thieves.
Somebody noticed Paul Machacek, who's a developer at Rare, listed Banjo-Threeie. Rare replied, "Paul. PAUL." Which I thought was cute.
That's pretty much it outside of musings. Gregg Mayles says he has no intention of being a part of a new Banjo game for the foreseeable future, though Rare could always license out the property to another developer. I think it's unlikely, I think, if anything, they'd do a remaster of the first two games like the N-Sane Trilogy, as was the original plan for Nuts & Bolts. But Threeie? I dunno, I just don't trust Rare at this time to make a Banjo game that remained true to their spirit. Though, with the success of Yooka-Laylee, it's probably been on their minds. If I had to choose, I'd rather Banjo be in Smash than a Banjo-Threeie, as I think Sakurai would stay true to their characters.
EDIT: Welp, this thread is moving fast. Guh-huh.