Urriak Uruk
Gaming is fun, and fun is for everyone
The Fizban Subclasses were 13 months, actually, but the Races were closer to the final release. But March is totally plausible for a September or November release, based on prior precedent, even for a Subclass. Race stuff tends to be a quicker turnaround. i think we will see Spelljammer in a few months, and Dragonlance in either September (as the yearly AL Adventure book revisiting the War of the Lance, with Setting elements) or November (if it's a more traditional Setting book).
I'm fairly confident the Spelljammer book has a strong adventure element as well. A while ago, Perkins teased the cover of an upcoming book, and it depicted Boo (the miniature space hamster) and a beholder. Although it could just be a setting book, I am leaning on it being an adventure with Minsc/Boo and something to do with the beholders in Realmspace (or maybe beyond).
Kind of like Ghosts of Saltmarsh/Wild Beyond the Witchlight/Descent into Avernus, having rules for new races and Spelljamming vehicles, in the context of an adventure.