My prediction:
Sierra will be Activision's "Non-AAA" sub label. All the games that are weird, niche, arty, experiments that push gaming forward just a little bit, ressurections of old IPs, and new IP's that Activision deem not worthy of $500 million in advertising over 10 years, will be published under The big rock. A glorious golden age of gaming follows.
The likely reality:
Mobile ports, one or two Mediocre new games, a couple of remakes, and a 3D nextgen King's Quest Reboot that's overhyped but tanks horribly.
I hate being a pessimist.