If there was one year they could have taken more than a year to push out a new Madden, it would be this one where there's no NFL going on for who knows how long. But I guess they want to be quick with a next gen version.
I imagine EA are not the only ones who will do this upgrade a limited time offer. Limited time may become the norm, but I can't really complain since it is free for a while, and it cost them money to do. Maybe not much, but still.