-This is a full on collaboration. It's not Nintendo handing off their franchise to another company; the Metroid staff are working on this to make sure it's going to be a true Metroid game (so hopefully we won't hear Dyson complain about how this isn't a Metroid game :D). The staff is making sure there's plenty of exploration to balance out the action.
-As the trailer suggests, there's more focus on the Metroid lore; Adam's in the trailer, so we're going to see what happened to him prior to Fusion. The other solder we see is one of his solders as well.
-This takes place between Super Metroid and Fusion.
-The other female at the end of the trailer isn't Samus.
The staff seems to be really enthusiastic about the title, and I'm really eager to see what they come up with. Here's wishing them the best!