Definitely mine most wanted veteran, next to Robin. Like Olimar and Alph, I'm hoping Bayonetta gets a Jeanne costume.
Assuming Smash Switch is not a straight up port, I could see her getting a tweak to her moveset. Personally, I wish they would change her back to how she was before the nerf hammer--only this time, her combos don't kill nearly as early. But since people are STILL whining about her, that's probably wishful thinking.
Bayonetta has a lot going for her. Nintendo has practically become her new home, with Bayonetta 2&3 being supported by the company. Furthermore, her games are top-notch. The first game is owned by Sega, whom has a good relationship with Nintendo. With Sonic the Hedgehog appearing in two Smash games now, it's pretty clear Sega has no qualms about having their characters in the game.
That said, I'll be surprised if she doesn't return, but I'd rather not jump to conclusions.