If these rumors are true, then this is definitely a big deal, not only for how it affects potential PS4 users, but also PC users (by tempting them to buy the new Xbox, even if they're running a high-end PC, due to a particular game that he or she wants to play). I personally wouldn't be surprised if Microsoft tries to secure timed exclusivity with all of the biggest FPS (Battlefield), RPG ( Bioware), and sports (Madden, Fifa) franchises, along with exclusivity deals with other Microsoft-leaning companies like Bethesda. Mass Effect was one of the big reasons why I purchased a 360 back in the day (largely because it didn't release on PC until later), and I'm guessing Microsoft wants to do something similar this generation.
I do find these rumors strange, due to how EA has recently had a good relationship with Sony, but money can easily change relationships.