I personally think it's a coing flip either way, as to whether he does decide to fight further. That being said, I think folks are downplaying the issue of control over when he serves whatever penalty is ultimately passed down. As it stands now, he's going to miss the first four games. If he decides to sue, he's at the mercy of the court as to not only how many (if any) games he sits, but almost as important - WHEN HE SERVES THEM. He has to weigh the very real possisbility that he ends up serving a two-game suspension in weeks 16 & 17, or worse, a four-game suspension and misses the entire stretch run - when he's needed most. People can say that's not a part of his thinking, but I can guarantee you that he not the only one doing the thinking here. Someone on his "team" has thought of this possibility, and you can make certain Hardy has been made aware of it.
Another thing that isn't being considered is his image. At some point he has to begin thinking about rebuilding his public image. Accepting the suspension as it is now would be one way to initiate that process. It's going to take more than that, but it's definitely a step in that direction. I imagine one of his advisors has made sure he's aware of this consideration as well.
I truly think that this is going to be the end of it. I expect him to accept the punishment as it is now, and move forward with the resurrection of his career.