Scott Burnside from ESPN has his predictions on where people will end up and has Boyle going to the Wings, Niskanen to the Caps, Ehrhoff to Tampa, and Stralman to either the Wings or Tampa.
I'd be ok with Boyle if we get Stralman. Stralman is a defensive defenseman and makes us stronger on the back end why Boyle can help on the powerplay for two years until Sproul gets ready.
I know people hate Boyle because he's older, but if we can get him and a younger guy like the scenario listed here... you gotta be okay with that, as pointed out already. We should be getting more offense out of Smith, too. So you have Kronwall, Smith, and Boyle who are more offensive, and then Ericsson, DeKeyser, and Stralman who are more defensively sound. I know, Kronwall is pretty well balanced.
Then you can filter in Sproul as Boyle departs...