EA have sent out a "save the date" notice for an event during GDC week that makes us think they may be preparing to reveal Battlefield 4. The colours, the nature of the image - it all points towards it. Furthermore, DICE have made it a sort of tradition to unveil their projects during GDC as was the case with Battlefield 3 for instance.
Naturally EA could be preparing to show something entirely different, but our money is on Battlefield 4.