So.. last season was pretty badass, but the finale maybe should've been a series finale.
Mitchell was killed, and it seemed like a fitting conclusion to the show. But the appearance of Wyndam seems to have set some new things in motion.
Apparently, Russell Tovey (George) is leaving the show at some point this season. And it seems like we'll be following several new and old characters, rather than it being focused on George, Nina, and Annie.

Toby Whithouse wrote:"As ever, Being Human lives or dies on the strength of the characters and the cast, and that's why I think this series is our strongest yet.
Damien Molony joins the team as Hal. Hand on heart, I think he's one of the most exciting and versatile actors of his generation. Watching his performance grow over the filming was a joy.
Then there's Michael Socha. Promoted from semi-regular to lead. If you thought he was good in series 3, wait till you see what he does in series 4. Michael will break your heart this year.
And of course beautiful Lenora. Our star. The heart of the show. This year she gives a truly breathtaking performance. One of my favourite moments of 2011 was the first full screening of episode 2, when she left us all with our jaws on our chests."

I am looking forward to the new season, but also kind of worried.. especially if George is being written out. This is a small show. I don't know if re-inventing it is a good idea.
Also, episode titles:
“Eve Of The War”
“Being Human 1955”
“The Graveyard Shift”
“A Spectre Calls”
“Hold The Front Page”
“Puppy Love”
“Making History”
“The War Child”
No premiere date given so far, but it will be end of this month.