If they only include 4 classes I won't be buying this game. So far that's what they've announced, too, so I'm not holding my breath they change anything.
That, IMO, makes it Bad Company 3, not Battlefield 3.
6 classes would be perfect, even 5 would be much better. Really need to separate medic and support classes, combining the two and giving the assault class the ammo drop is just retarded.