I guess Layton decided to go to Yasogami High School for some continuing studies. It seems like a bit of a downgrade after teaching at Gressenheller, but it's important to diversify your education CV.
I mean, I don't know what fighting game ArcSys would do that would involve Layton (unless Cross Tag Battle goes completely wild with future DLC), but I'll never object to ArcSys making a fighting game including proprieties I love! ArcSys are truly masters of their craft.
Anyway, regarding Layton in Smash, I'm feeling cautiously optimistic. I am imagining the next 6 characters may be a bit more first-party-heavy, but if there is another Japanese company that makes sense in Smash and doesn't have non-playable representation already (i.e., not Koei or Marvelous), it's Level-5...