Some brand new details have just come in from E3 2011 regarding the classes that will be in Battlefield 3 when it launches later this year.

The four classes have received an overhaul in the latest entry and a breakdown of each can be found below;

Assault/Medic

The Assault and Medic a classes have been combined now, where the
Assault class can either chose to heal/revive teammates, or you can opt
for a grenade launcher instead of the revive kit, if you want more
firepower.

Support

The Support class is now the one handing out ammunition, and can also
provide covering fire. You can mount your LMG and if fire in the
direction of the enemy, youll get special bonus points for providing
covering fire for your teammates. You can also select an assault rifle
with a flashlight for the dark parts of maps (like tunnels), instead of
the LMG.

Engineer

The Engineer retains much of his role and load-out from Bad Company
2, youre equipped with rocket launchers against enemy armor, and a
repair tool to fix friendly vehicles, and a sub machine gun.

Sniper

The Sniper has the same role as in previous Battlefield games, and is
armed with a sniper rifle, C4 explosives, and spotting gear.

Source: Bf3Blog