The content update is scheduled for early August and adds a new training gym, new equipment to put on your created fighters, and additional sliders for gameplay adjustments. In the Xbox 360 version of this update, players will also receive an alternate version of Sugar Ray Leonard. The press release is sure to mention that Sugar Ray comes to you courtesy of Pizza Hut, which I can only take to mean that he'll wear P'Zones on his hands instead of gloves.
A separate update due in September will make adjustments to the control options, allowing players to use the face buttons to throw punches. All I can say about that is that anyone who uses this button scheme is a straight-up sucker who is robbing themselves of one of Fight Night Round 4's best aspects. Are you that dense that you can't pick up the existing controls, which have you use the right analog stick to throw punches? Seriously, it's not tough.
Anyway, the new control options seem like the sort of thing that could imbalance the multiplayer. If that's the case, hopefully there will be some kind of online filter. I checked in with EA to ask about that, and the company's response is "we will make further announcements surrounding the button controls in the coming months." So we'll have sit tight and see how it goes.