In this image put out by BioWare they seem to be pointing to four (4) classes that we can be. Two (2) we know of, from left to right, the Colossus, Ranger and the two (2) we we don't know the names of. The exo suit or javelin to the far right is different from the other three. Notice that this Javelin does nor a have jetpack but held aloft by energy generated around the legs. I'll explore this Javelin in the following images.
Here is the full squad of four players and as you can see they each have an element associated to them and a percentage next to that element. Paul is the Colossus and Michelle is the Ranger. Kim and Sandra have two different looking helmets, but at this point we don't know what their class is. I would guess that they are a lighter build than the Titan or Ranger.
This image shows Kim arriving to form up the squad in the classic hero landing.
This image Sandra arrives, but notice she teleports in which is different from the other three.
This I believe is Sandra's Javelin and the only one that appears with a hood and cape and has three different elements connected to the right arm. Plus there is no jetpack. By the look of this Javelin this may be a very light build but designed for a unique roll within the squad. It seems that BioWare has given us some interesting choices, two standard but two may be unique. I'm sure all will be fun to play.