Also, where does the Creation Engine fit into all of this?
My guess is it Fits in 3 years ago when it was being created.
But, The creation engine is built with Directx11 capability[?], just not using the features. It's entirely possible (and likely) that the new console will be a DX11 platform, and that the creation engine can be augmented later to take advantage of all the yummy in my tummy power, for a Fallout (4) at the early-middle of it's run.
Assuming these rumors are even true, that a new Microsoft console is on the way by 2013, It almost goes without saying that BGS would have been aware of that anyway, and they still decided to work on the 360. Considering how important Launch titles are for new Hardware, it would be Prudent to get key developers aware of the tech jump years before the public, so as to launch on a strong note.