I wouldn't give up one 1st round pick to get Mack in Miami. Dolphins are too far off to be pinning thier hopes on a 29 year old pass rusher. At this point I would rather have one good 24/25 year old pass rushers or two just decent/promising 22 year old rookies that have more years in the tank. Plus Mack would not be happy spending the final years of his prime on a team in the early stages of a rebuild.
Nothing on his twitter timeline, so probably someone making fake tweets.
I did see something this morning about Mack being used as trade bait for the Redskins for their no.2 pick, but sounds pretty unlikely to me especially with his cap hit and the Bears having a young QB (who's not that good admittedly).