Tim Britton has a piece on Daisuke Matsuzaka and how Dice-K's next start will not only be the last for the 2012 season but also his last in a Boston uniform.
One thing that Tim doesn't point out is that Dice-K has actually been better away from Fenway in his MLB career (4.76 ERA in 57 Fenway starts vs 4.19 ERA in 58 career road starts). I think Dice-K, if healthy, could be a very nice pickup for another team. Many teams would be happy will a third or fourth starter posting a 4.19 ERA. And if Dice-K winds up with an NL team - then it is not too unrealistic to see that ERA in the 3.50 range.
I just wouldn't sign him to a longterm deal - just in case I'm completely wrong.