It's not going to focus on Shaw, that's for sure. You can't make a movie with a single woman and an android's head. I mean, you can - when you're making a low-budget s-f like Moon, but not when you hire Ridley Scott and give him 100 million bucks to waste. It's gonna be mainstream and mainstream needs lots of dialogue and some cannon fodder. So I guess it'll be about searching for Shaw, and in the end they're gonna find her on the engineers' planet, then fight some monsters and explode the planet.
Really, this series is rather predictable about its endings:
Alien - big explosion
Aliens - big explosion
A:R - big explosion
AVP - big explosion
AVPR - big explosion
Prometheus - big explosion
Geee, I wonder what happens next.