In a new rumor reported by CVG, who claims to have two separate sources that confirm the matter, Microsoft & Electronic Arts are set to announce some kind of exclusivity deal for the next Xbox console.
With cross platform publishing being as important as it is for a company like EA, it would be extremely unlikely for all EA games to become exclusive to the Xbox, although it would be a huge coup for Microsoft if that was the case. EA's franchises include series such as Need For Speed, NFL, NHL, Battlefield, Mirror's Edge, Dead Space, Crysis and a lot more. It seems more likely that this will be some kind of timed exclusivity deal, most likely for DLC rather than full game releases. Think the Activision deal where Call Of Duty DLC releases a month earlier on Xbox.
Full details on this deal are planned to be revealed at the same time as the new Xbox, according to the rumor. Current grape vine talk suggests that will be some time in April.