I still think they are going to name them Banjo & Kazooie. I feel like them being called Banjo-Kazooie would be weird to hear the announcer say.
Then again Europe was the only smart region to name Duck Hunt as Duck Hunt Duo so I don't think they care about weird name setups.
Smart to name them Duck Hunt Duo? I'd argue the opposite. They would have been smart if they named the characters Duck Hunt
Trio... but they didn't.
Duck Hunt as a group name is better than Duck Hunt Duo because at least Duck Hunt doesn't lie about how many characters the group is comprised of. Even the NoE version of Smash 4/Ultimate has the Palutena Guidance difference that says something along the lines of "While they're called Duck Hunt Duo, they're actually a Trio." If they're actually a trio, why would you call them a duo?! It's ridiculous and not in the good way.
Honestly, all regions should have either called them Duck Hunt, or Duck Hunt Trio. (The Japanese version calls them Duck Hunt)
/rant
On the topic at hand, in my opinion, the name of Banjo should just be Banjo-Kazooie. For instance, Olimar in the Japanese versions of Smash is actually named Pikmin & Olimar, but shortened to just Olimar in the NA version. Rosalina & Luma takes too long and does not roll off the tongue. Most people shorten it to either Rosalina or Rosaluma. No one likes saying the full name.
Remember, it's a group name: "he's Banjo and she's Kazooie, together they are: Banjo-Kazooie!" You have to treat it like some sort of musical band. Remember the Ice Climbers aren't called Popo & Nana, heck in Japan they're not even called Ice Climbers, they're just called the game's name (Ice Climber), just like Duck Hunt is. Banjo-Kazooie isn't even remotely strange in this instance and actually matches up with prior naming-schemes.