I ran the update for Mavericks as well as the Xcode 5.1 update (build 5B130a) and I can't find a way to update my OS X SDK from 10.8 to 10.9 (The only updates that show up are iOS SDK 6.1 and the docsets).
I was looking forward to using Sprite Kit on my Macbook Pro (10.9.2), but the SDK just does not show up. SpriteKit is definitely on my system, though, because
/System/Library/Frameworks/SpriteKit.framework/ exists. When I add the SpriteKit framework directly from
/Applications/Xcode.app/Contents/SharedFrameworks/SpriteKit.framework it can't find it either.