I'm not comfortable giving up 4 more years of a great young MLB player in Travis, and one of our top prospects for another guy over age 30.
Yes, I know how good McCutchen WAS, but there is not guarantee he bounces back. He was A LOT worse than his career norms last year. A LOT worse. Couple that with the fact he's on the wrong side of 30, I would be cautious to give up Travis + Alford for him.
You look at guys like Tulo and Martin, who have gotten worse past age 30. McCutchen might now be in that group. This team needs to get younger, not older.