Lol, its not naive, its common sense. Of course they look at what Sony is doing, but the rumour of
QB getting delayed came before
Uncharted was delayed. They aren't going to make a big development/line-up decision like that based purely on Uncharted, a decision which could also cost them millions of dollars in extra development time.
A new IP like QB or pretty much most new IP isn't going to be able to compete against Uncharted, which is the 4th on mainline consoles and 5th including the vita, a very well established brand.
MS have a packed holiday and said back in late last year they are going to have to move things out of the holiday. Makes much more sense to do that with your new IP (particularly after unfortunately SO didn't set the world alight in the same period) than it does for your other titles, they clearly weren't going to move Halo, Forza or TR.