I had supported exploring trading Dempster last summer. I knew he was a capable pitcher at the time and was a nice clubhouse personality, but I felt that at his age he was likely to deteriorate from effectiveness before the Cubs became contenders. In retrospect I wish they'd done that and gotten some younger talent from him from a team that needed a pitcher.
The good thing is that he's losing his stuff before Hendry extends him. He's owed only a little over $30 million for this year and next, assuming he accepts his $14 option for next season. (Less than $30 for 11-12 originally, but he deferred some to help make some space for Hendry bring in Grabow and Pena).
With Dempster having an option after this season, if he'd have held up a little longer Hendry might have been tempted to extend him for a couple more years. So maybe it's just as well that he falls apart before Hendry has the chance to make that mistake.