The game does not have an ending, but its competely playable, and since it does not have a real story the ending is just the boss of the last biome they added. There are no "holes" in the content, the endgame is expanding each patch, thou its pretty slow.

In this sense it has been playable since release years ago, There is no real reason to wait for "full" release. Also game has mods already, if you want more content.