When did development start on this? And how many years before it's finished would you guess?The single player campaign will hopefully release by the end of this year.
The MMO part will release in updates. 3.0 will be released in the coming months.
4.0 seems about the time it'll feel like a full game and that will be 2018/19 probably.
After 4.0, there are still a lot of features planned.