Season 2
Honestly, 8 episodes seems rather short for a season. I'm surprised season 1 didn't have 10 episodes like Orphan Black or 13 like Atlantis.
That said, I'd like to think it'll return given Orphan Black has pretty similar ratings. It's not like that gets a whole lot of viewership either and I think this is better than Orphan Black, which I've been following since the very beginning.
Sometimes it takes a network awhile to renew a show. Look at SyFy. It took them a few months to renew both Haven and Dominion for a second season. They were on the fence with both of those shows. It may be the same way with BBC America and Intruders.
I think cable channels in particular have more of a leeway when it comes to something like this, as they know they're not going to pull the same kinds of numbers the major networks are going to pull when it comes to shows. I've seen shows cancelled by TNT, USA, etc..., but they've generally lasted far longer on those channels than they would've had they been on a major network. Major networks are much quicker to cancel and make the decision to do so quicker. They'd rather not give something a chance than try to give it a decent chance with the audiences.