Of course, but you can't outline it ahead of time, this would have to some form of "Discovery Writing".
And it would reflect life. Just like "Roots", it dramatized the ancestorship of a Black American from the 1700s forward, for several generations.
It begins with a baby born in Africa, his story and culture as he grows up, becomes a young man, but is then captured, shipped to America and sold as a slave. And we follow him and his sad, violent life in slavery.
Although truncated in the movie, we follow his story. Eventually he fathers a child, and we see the child grow, with their own personality and talents. When the child is sold, we switch to the child's view. The original protagonist dies, the child is the new protagonist, we see their story, they grows up, have a child, and we repeat, moving ever forward into the future. As the culture changes with each new protagonist, as slavery ends and Jim Crow begins, etc.
That protocol is endless, for as long as you can write, and invent new stories, and a changing culture. Roots is a fiction grounded in actual well-researched history, but you can write a complete magical fantasy realm, as Tolkien did, and carry it forward as far as you like.
You don't have to get "technological" or "SciFi". Our civilizations existed without even electricity for thousands of years, our technological age only got started a few centuries ago, with about 9 dozen centuries before that of very low-tech "civilization".
So certainly a magical realm could go on for thousands of years, following a descendant line like Roots, that become everything from kings to paupers and all in-between, good and evil protagonists, smart and dumb protagonists, lucky and unlucky protagonists.
For as long as you can write, and you still need not be "finished" with the story, it could be passed on to another to keep it going.