If you buy the Fallout 4 Season Pass, you're entitled to Automatron, Wasteland Workshop, and Far Harbor. You're also entitled to Contraptions Workshop, Vault-Tec Workshop and the much larger Nuka World DLC.
Nuka World is scheduled to arrive in August, August 30th is the rumored release date, and the $20 add-0n figures to be the second largest add-on behind Far Harbor.
Unfortunately, Bethesda says that Nuka World will be the last piece of downloadable content it releases for the game. That could change but at this point the door appears to be closed.
Once Nuka World arrives you'll want to turn your attention to the vast collection of mods on Bethesda's marketplace. There, you'll find new weapons, quests, and more.