Honestly, when it comes to Halo 4 (and the whole new Halo trilogy, really) the only thing I care about is what they're going to do with the story. See, I'm one of the very few Halo fans that actually plays for the storyline alone (and yes, there are many here that would turn their nose up at the story because it's not original enough. Of course it's not original, it's a space shooter >>). To me, Halo 3 was a slap in the face because it pandered to multiplayer fans.
Anyway, to answer your wonderings with similar wonderings;
1. There will most definitely be new weapons. It's a new Halo game where they're going into this... portal? There's gotta be new things.
2. I'm counting on a mostly Flood type game. I mean, it's an ancient evil. Unless the Flood has some best bros called the Sun or some crap, it's probably the flood. Maybe new forms. In fact, definitely new forms. Vehicles? Not so sure about.
But the trailer is very promising, and although I was hurt very badly by Halo 3... it's a new company and I'm dying to see what they can do.
But the thing that I really want to know? If this is going to be a Forerunner centric plot. And none of that Cryptum Forerunner junk. Like, real awesome Forerunners. I'd be super excited forever if they did a Forerunner plot right |D