This is a list of known information about Factorio's "one big expansion pack".
- Q: What?
- A: It is way too early to show any of the plans, and since we want to keep the iterative process of expanding things that prove to be the most fun, the plan is quite loose anyway. 
- Q: When?
- A: All I can say is, that we are starting work on it now, and we don't think that it will take less than a year to develop. I'm personally very curious how the theory of getting more efficient once the engine is solid will hold. 
- Multiple people, including the modder Earendel were hired to work on the expansion pack, more positions are open.