Blizzard have released their "roadmap" for the coming year, showing known (and unknown!) forthcoming new content, and the new expansion rough release dates.
You can read the full post on Wowhead but for a short version, relating to Retail WoW:
In modern World of Warcraft, you’re going to see three more content updates for Dragonflight arriving before World of Warcraft: The War Within releases next year. In these updates, we’ll be wrapping up the story for this expansion and laying the foundation for our next one. Dragonflight Season 4 will revisit Dragonflight’s dungeons and raids, along with outdoor content, featuring updated rewards, and a few new twists. Then, in the Spring/
Summer, we’ll ask for your feedback when the War Within expansion alpha and beta tests drop. We will continue to communicate details, dates, and more goodness as we get closer to content updates, just like this year! Well, most of it anyway (we’ll have some surprises in store too!). Coming up next in January, we have the Seeds of Renewal content update on tap and we’re currently keeping an eye on your feedback on the live public test realms (PTR) for this update.