The XCOM website has been updated and has some other small details:
The mobile base is called "The Avenger" and is a converted alien ship.
There are five classes now — I'm guessing "Ranger" is the new one. They mention "Momentum" as a new class ability.
"The state of the world affects each combat mission's environment."
"Use concealment to ambush enemy patrols."
"Loot enemies for precious gear and artifacts."
You can save fallen soldiers by carrying them to the extraction.
"There are virtually infinite combinations of map, missions and goals."
Also confirms head-to-head multiplayer on generated maps.