It could be for releases but Necrons being included makes no sense. They are nowhere near due an update. Unless GW has decided it's time to drop the nerfhammer. For a moment, I thought they might be signifying which armies would be getting Mega Battleforces this year. But they usually only due a couple and not including some kind of Marine one would be unusual. Orks and Nids would be nice to see for this but again, Necrons just had one. So maybe my conjecture will help somebody figure it out. Otherwise we just wait.
"Fetch me another plaything. This one seems to have broken." -Urien Rakarth
Space Marine- "This planet is ours, witch."
Eldar- "No ... This planet is theirs ..."