We are coming close to beating good teams without him. We need a huge presence in the middle to turn the corner. His lack of height and defensive intensity will always haunt him. If he were 5 inches taller I'd give it to him. Not saying he's not a great player. Just that 25 million/year is way too much.
There may be teams out there willing to pay him that much. But, I doubt there is a lot of them. It's possible he'd regret signing elsewhere for he may end up in a situation similar to what Evan Turner is in this year, i.e., he is making great money, but his usefulness has taken a big hit.