Angel and Chaos Marine units we may be getting.
Please remember that this is a rumor, no official announcement has been made.
Starter news I have heard from several places now:
Ravenwing bikes (3 likely)
Dreadnought seems likely, as it adds vehicle rules. CSM squad may be referring to the chosen, or may not. Posessed will have to see, but they would add a daemonic aspect to the force.