I was thinking that the Red Sox might trade for a starting 1b, and play Kyle S. in LF, and, yes, use Duran as the 4th outfielder the rest of the way. It is quite possible that is the plan, but to see evidence of that plan we would need to see the Red Sox obtain a starting 1b today. If they don't obtain a starting 1b, we can safely assume Kyle S. will play the position and Duran will continue to play in CF.
I think Duran continues to play and that Kyle S. was acquired for 1b. The key point here is that by upgrading the offense at 1b, the Red Sox can simply drop Duran down to the ninth spot, they don't need him in that second spot anymore. Duran may struggle but he can survive as the ninth hitter. Even though he is struggling, he can help you with his amazing speed, and he has proven that so far. Thus, I think the Red Sox will keep playing Duran but they will bat him ninth and the acquisition of Kyle S. allows the Red Sox to move Duran down the order.