Its their IP, they can do with it what they want. EA is generally an "All Platform" publisher. I bet MS spent a ton of money to keep TitanFall(TF) XboxOne (X1) exclusive in perpetuity. But look at it this way.... MS had a very rough start with the X1. When TF was announced, and teased, it got a TON of positive press. It is one of the most anticipated titles for next gen. MS saw this, and said, "What better way to sell a ton of new X1s than to exclusive this title. Also, they could, if they wanted, make it also a W8 exclusive.
Another option with this exclusive would be to make PC and console gamers play together. I think this would be a great title to make that happen myself. It could also be another way for MS to push W8. "If you play TF on W8, then you can game together with the X1 players!
Just my 2 cents. I would like change for my nickel now.