Well, she says it's not certain that Season 4 will be the last. But she also says she doesn't know if it will continue after that. Though she definitely knows, as she knows how the story will be, and whether it ends with a cliffhanger or not.

Well, I'm a little glad to hear that it's still going.

What's more to be done? What more storylines can there be?

I'm not quite sure if this also indicates the ending of svtfoe but a crew member tweeted that it was their last day working for the production of svtfoe. Link: twitter.com/beckyandfrank/status/1010357156510461954

Actually this Cartoon has a deep lore with It's 2 books they can keep it going as long as they want.(But ofcourse there is a disney season 4 problem I hope they will solve this!)

Daron refuses to confirm if this is the last season or not

i assume she wants another season, but working it out with disney is tricky.