The answer to this question is known only to Iron Gate Studio and possibly not even to them.
There are three biomes which currently exist only as place holders (Mistlands, Ashlands and the Deep North) and another, the Ocean, which may undergo major changes. The three place holders will each contain a boss, which a viking must defeat to finish the game.

As far as I know, Iron Gate Studio has not indicated if defeating the final boss and securing Valheim for Odin will result in a cut scene and a reassignment to Valhalla.

If you mean to ask "Can you continue playing after defeating all the current bosses?" the answer is yes. One might prefer to take a break pending the release of the next complete biome. I will probably continue playing to maximize my equipment and skills. Perhaps even to build a really elaborate base or some outposts closer to one or more of the placeholder biomes.