I believe that a minimum of $7.00/share or roughly $1.5 Billion would be the minimum the company would consider. Potash and Mosaic are sitting on piles of cash and this would be an easy fit for them. A combination of cash/stock could also be a possibility. I personally wouldn't mind an all stock deal, considering the price these companies stocks are trading at. A higher premium might me obtained if it was an all stock deal.
Anyway, this all seems like wishful thinking, but....It sure is nice to think about it!!