I think Treyarch will follow it's usual timeline, after releasing 3 map packs for WaW they didn't make another one because MW2 was right around the corner. It will most likely be the case with MW3 as well. Also, it wouldn't make sense if they release another map pack... If they release maps in late september (28th) for Xbox and Octobor 28th (PC&PS3) and with MW3 right around the corner in November no point in really buying the map pack for PS3/PC players... The only logical reason for Treyarch (Activision's decision really) to release a 4th map pack is to probably keep the "COD" series interest high during the August - November time line when A LOT of high interest games are released... like Uncharted 3, Battlefield 3, Assassin's Creed Revelations etc...