Please let it be local co-op with online elements like the first one. Hands down one of the best experiences playing with a buddy in the same room plus 2 helldivers online. As for the third person aspect, it remains to be seen how that will play out. Fingers crossed!
I'll surely check it out when it's released, but from these trailers, I can't shake the feeling, that the top-down View was a better fit for the stealth and combat mechanics. Espescially since it looks like they simply ported HD1 into third person. I was really curious how they change the mechanics when transistioning to third person, but from what I can see, they just didn't.
I think it looks really good so far - very true to the original game. The only thing that looks a bit underwhelming is the environments. I'm guessing they're procedurally generated but so far they look a little dull. Hope I'm wrong though.