The new Raven wing novel, gives some clues on what new units may appear in codex Dark Angels.

Black Knights: Veterans of the Ravenwing possibly an honour guard for Sammael.  Mounted on bikes (not jet bikes sorry) equipped with plasma weapons. Lead by a Huntmaster and all armed with Raven headed Thunder Hammers.

Vengeance-pattern Land Speeder: A new class of Land Speeder armed wiht lots of plasma weapons.

Darkshrouds: Based on a normal Land Speeder. They carry a plasm powered shrouding devices in the form of a statue from the Dark Angels fortress. The field is mean to be large enough to cover a landing Thunderhawk.
Dark Talon fighters: Armed with Hurricane bolters  (no clue on appearance or transport capacity)

Nephilim fighters: Armed with Avenger bolt cannons and Blacksword missiles, (again no clue on apearance)

cswang  on Warseer 1st spotted this.

Remeber these units are now offical background so may or may not be in the codex.

Ben