I do hope they hold true to this statment; FL and DS were too small.

Guest-214: Mists of Pandaria features an ambitious number of 18 raid bosses and I'm very excited about that. Im curious though as to how many bosses we can expect to see in future tiers? Firelands and Dragon Soul felt like small tiers with only 7 or 8 encounters in the tier.
IonHazzikostas: To Guest-214 We like big raid tiers too, and will do our best to continue delivering them. We're planning for the next tier after Heart of Fear/Terrace to be a fair bit larger than Firelands or Dragon Soul were.