Marlins aren't trading Stanton anytime soon, especially with the possibility the Marlins could contend next season. And the Marlins will want something a lot better than what the Sox have on the farm if they're trading Stanton, preferably a power hitting OF. Swihart, Betts, and their pitchers won't cut it, especially when Miami has enough young pitching prospects in the system.
And Cespedes is a free agent in 2015, and not the kind of player Miami wants. They want MLB ready and controllable talent for Stanton, not expiring contracts.
In addition, the player's union and Rob Manfred will likely block any Stanton trade, because of what happened in 2012 after the Marlins had their fire sale, likely pushing for the Marlins to ACTUALLY make an attempt to resign Stanton.