Banjo is a tough one for me. I played their games obsessively growing up. Kazooie and Tooie are among my favorite games of all time, and I still make it a tradition to replay them annually. I even enjoyed Nuts & Bolts, the GBA games, and backed Yooka-Laylee day 1 (don't regret it by the way, the game's strengths are far more numerous than its flaws). And second only to a certain crocodile monarch also made by Rare, B-K are and have always been my Dream newcomer.
However, pretty much since the buyout happened I've written them off as impossible. The introduction of third-parties in Brawl and then Smash 4 was a small spark of hope, but it seemed one third-party or another kept beating them out (first Mega Man and Pac-Man, then the three DLC). So while the pool of big name third-parties is thinning, the competition is still vast for Banjo and Kazooie. Especially if Simon Belmont ends up being in, not to mention there still being other contenders like Geno, Rayman, Crash, and possible third-party Echo fighters.
I'd say their best chances would if Minecraft got content in this game that wasn't Steve (like a stage or item), and Banjo-Kazooie was negotiated during that time.
Well, I'm done writing this as I've been looking at Dr. Doom kicking somebody in the face dozens of times, but I'm here to share my support for the bear and bird. I'll be over the moon with joy if K. Rool gets in, but give me Banjo-Kazooie and I'll feel like a kid again.