The Blacklist : you think

Katarina is the one behind the attacks? Maybe she's truly alive

Maybe, it's always possible. But I'm not sure they would introduce her as a villain so soon after Kirk. (But if they think the series doesn't have much longer to live then maybe they would introduce Katerina to tie up loose ends.)

I don't know about Katarina still being alive. I used to believe she was, but Cape May changed that for me. At the end when Red was having delusions/flashbacks or whatever, Katarina was forgiving him for saving Liz instead of her, she said she was alive through Liz. And by saving Liz/Masha he had saved her too. So I'm thinking Katarina is truly dead at this point. But it's just my opinion of course.