A class system has been confirmed. The developers have been keen to emphasise that the class system will be very free-form and unrestrictive.
Matt Higby suggested that classes will enable players to recognise enemies more easily, and give players a better idea of their role in the battle. All classes will have significant scope for personalisation and specialisation.
This list has been suggested in a Q&A but is not necessarily complete, accurate or final:
We know that healing and repair will be done by two distinct classes, probably medic and engineer respectively. This means, for instance, you will not be able to both heal and repair at the same time.