Originally posted by Rhapsody:

It's not fully disconnected, but I don't remember the details. The Forsaken are shaking Valheim around which is causing trouble further down the trunk of the world tree.

Perhaps still connected in the game lore but not actually connected in game. You won't (currently) find a connection to the world tree or the rainbow bridge by sailing all the way around the Valheim world or exploring it's entire surface (or by using freefly and going up or down through the terrain).