When Everwild was officially unveiled last year at Microsoft's big Inside Xbox showcase, we actually learned very little about the game, which, at the time, was early in development. It does seem like Rare is continuing to work hard, and perhaps now we've learned just a bit more about what the final product will entail.
This potential new information comes courtesy of a new trademark filing for the game made by Rare and Microsoft, which specifically mentions the game as a so-called "SaaS", or "Software as a Service", which must mean that Microsoft is aiming for this to be what we are more used to calling a "Live Service" game.
While the filing does not specifically mention how the game incorporates these structures, "Games as a Service" is generally understood to be a service rather than something standalone or a one-off, meaning that it sounds like the plan is for it to be continuously updated with content.
Of course, Rare has already dipped a toe in this area with Sea of Thieves, so the team certainly has the experience to make something like this work.