Leake? Meh. The very definition of an average pitcher. He didn't exactly flourish with the Giants, at an extreme pitcher's park with an excellent infield defense behind him. He was a good guy and could hit homers alongside Bumgarner, but I'm glad the Giants chose to bet on Samardjiza's upside instead.
I don't see the Giants playing at the top of the outfielder market. Cespedes would be fine if the Giants had unlimited wealth to draw from. I don't want Upton: he'll get too much money for not great production or defense. Gordon is a good overall player, but the type of hitter that AT&T Park just kills. Dexter Fowler is okay, but would cost a draft pick. Gerardo Parra is nearly a clone of Gregor Blanco. The two outfield bats in the Giants' farm system that are ready to try to stick in the majors are Mac Williamson (good defense, some power, can he hit big league pitching consistently enough?) and Jarrett Parker (good power, millions of strikeouts, mediocre defense). I put my money on Mac, but I still expect the Giants acquire another OF one way or another.
It's a bit too early to count any of the top teams out for 2016. Still lots of free agents on the board, and I expect the Dodgers to actually successfully complete a couple of big trades to significantly strengthen their pitching staff. The Royals may have a hard time keeping their core together, but they will have more money to spend on that in upcoming years if Gordon leaves now.