Xcode Update SDK to 10.9
I accidentally forgot to rename Xcode 4.0 and left it as Xcode.app in /Applications/Xcode Older Versions/ which is what I used to store Xcode 4 in case the old Xcode 5 developer previews had any issues. So that bundle was replaced, not 5.0.

The weird thing is that even when I was sure I had it 5.1 open SpriteKit Game didn't show up as an option. Rebooting fixed that.

Oops.