I really hope you are joking. Even assuming you got Heyward to agree to a contract extension before the trade (not sure how that works), do the Twins really want to trade Meyer's or Berrios's three pre-arbitration years plus three arbitration years for another huge contract for five-six years? And while we do need outfield defense, we need starting pitching even more, especially after next year when outfield defense (Buxton, Rosario, maybe Kepler or Walker) is scheduled to arrive. And if Heyward can't agree to an extension, then this would be the stupidest trade ever. We are not even competing in 2015.
I'm not joking. To get Atlanta to move on Heyward would require that cost. I'm not saying it would be wise for any team. If any team comes to Atlanta on Heyward, they're going to pay a king's ransom to move him because the team is wise enough to know that's the only way their fanbase would accept such a move.