1.How many devs are working on this game? Is it 5?
4.Is this their main job?
Four, but only one, Alex, full time.
2.For how long is the game in development?
Since 2010.
3.Is this their first project, do they have some others?
AFAIK it's Alex' first major project after several smaller ones. David worked and Dungeons of Dredmor and now Clockwork Empires over at Gaslamp Games. Stian did the music for several indie titles.
5.Is there any plan for how much the game will be in development?
None that I'd know of.
6.I see there will be outposts, (planet battles maybe?), so how complex can we expect it to be on global? Will it be a more simple version of games like X3?
I only played the first X, but compared to that I'd say is will be more varied and complex in the end. The combat already is.
7.Are there plans for quests, like bounties and similar?
8.Will there be a main quest line that you can follow if you want?
There might be quests, but the main focus of the game will be on sandbox elements. You know, dynamic political and economical system the player can influence with his actions. If there'll be a main quest line is unknown, but given the lore premise it seems rather likely that the story will be concluded ingame one way or another.