We just don't know. It's done when it's done. The devs are busy with improving and adding all kinds of parts of the game, but they rarely say what they are planning next, and they say even less about when to expect the additions. They don't say what they do to keep the update a surprise each time and they don't say when things are done cause they usually don't know themselves.
Personly I don't expect much more skills to be implemented soon. I have the feeling that things like more maps, new skins and more and better quests and additions to the crafting system can be expected first. Updates are usually every two months or so. Patience is the key word.
