The interesting thing about sports game design is that they have long term and short term planning all on the same title. So you might have a team working on the next release doing minor tweaks, but you also have people working on a new iteration of a game engine that might take three years to finally implement.
But each year you tend to have one big focus point for improvement. It might be a franchise mode, multiplayer, or the core gameplay controls. With such a short development, you can only do so much.