Actually at the moment there five world bosses. I've only two down on my server and this by ~680h playtime. Other people are playing faster than me, they kill the bosses in a speedrun and they cry there is not enough content and they get bored...
I have a lot of fun to collect ressources, to build buildings and I have time to kill the other bosses.
A real ending isn't there at this time, because the full content ( (I mean) five bosses more) are missing at the moment.
Further a few bioms aren't ready, you can get inside, but there are no enemys inside.
I don't know if Odin take you with him, when the last boss fell and the game ends here, or if there is an open end. We will see.