Well, I'm neither a stock market guru or energy industry expert, but the Mississippian is the hot play right now. So the simple fact they have such a large footprint there makes them an attractive takeover target.
SD stock price is much more depressed than it should be according to TPG, and they have some legit gripes. I imagine they believe they can unlock a lot of value in the company that hasn't been tapped. But if the stock price doesn't go up in the next 9-12 months, I would think they would push for a sale.
Just my 0.02.