Parmandur
Book-Friend, he/him
Well, partly depends on what constitutes a "cameo," I suppose.Thanks, I forgot that timing. I wouldn't be surprised if the cameo is no bigger than what Fizban had for Dragonlance, though. Maybe Planescape or Greyhawk cameoing within Spelljammer?
Could also be another Adventure Anthology a la Tales From the Yawning Portal or Candlekeep Mysteries, or something more along the lines of Ghosts of Saltmarsh (more than an anthology, less than an adventure path or setting guide).
The new Starter Set isn't much of a known factor yet, but people have already noticed that it seems to have the 80's cartoon cast on the box. Maybe that will be nominally set in Mystara, or something weird like that?