I predict they will release at least 2 more flavors (or regurgitate old ones) of Space Marines before they get back to releasing the missing Necrons.
Note: There are already VERY NICE 3rd party Tomb Blades and Triarch Stalkers avaialble on the web.
Vote with your wallet - get the 3rd party models. Play at your FLGS and use them in any fun local tournament.
It took me all of 20 minutes to make an inexpensive mold of my existing Scarabs. It now takes about 15 minutes to make 10 new scarabs that look exactly like the old ones. Add 3rd party bases for 1/4 cost and you too can have a mass swarm of scarabs...