Maybe this is because I've never liked forge (I'll be honest, I hated Halo), but I really don't feel as if it would fit. They're already forging (no pun intended) a full, open world. It wouldn't make sense for players to just be able to make a map. Are planets just going to randomly appear? Or are there just gonna be moon bases that are invisible except under certain circumstances? I just don't think it fits in the whole "open world" concept very well.