Apparently due to player feedback, the new MMs starting with MM3 will have more flavor. (Including a section detailing WHY the various allies in the encounter groups work together.)
A citation would be nice.
WotC_Trevor on Twitter said:3. Monster Manual 3 hits in June! (People oooohing at the image of the orcus "miniature" )
2. We got feedback that the MMs didn't have enough flavor, so we're changing the format. We'll be putting a bit more story/hooks/descriptions..
1. for monsters to give it more of a story.
A citation would be nice.
Trevor_WotC said:We got feedback that the MMs didn't have enough flavor, so we're changing the format. We'll be putting a bit more story/hooks/descriptions..
for monsters to give it more of a story. #ddxp
criticalhits said:Monster blocks will contain a section on allies, and why they work together.
Info came from the various twitter feeds covering the D&D Experience. It's from the first seminar- the Wizards_D&D twitter feed had it (which I think Trevor_WoTC was using at the time.)

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.