Too small of a userbase. They can port to the PS3/PS4 later in the year.
I get that my point was that as an exclusive (timed or otherwise) clearly primarily aimed at next gen by MS it makes more sense to launch it on the new console only - look at Gears as an example. I can definitely see EA wanting it on 360 (and I'm sure it is timed due to EA link as well) but it means at launch it won't necessarily drive a lot of people to pick up an XB1 for it if the experience is decent on the 360 they already own.
New consoles need games only available on them or as minimum a clear move like EA allowing BF4 upgrades - maybe this will emerge for TitanFall too closer to launch which would make a lot more sense in that case.