MB Passion writes the new E-Coupe may be 12 cm longer and 7.5 cm wider than the predecessor and the rear leg room may increase 6 cm. It's expected for NAIAS in Detroit in January.
http://www.germancarforum.com/threads/next-gen-mercedes-benz-e-class-coupe-convertible.50737/page-22#post-813752
http://www.germancarforum.com/threads/next-gen-mercedes-benz-e-class-coupe-convertible.50737/page-23#post-813768