I don't think an Xbox Slim will happen because of 20nm but a new chip is the catalyst for a new board so why shrink the whole thing.
The Xbox One was originally designed to be an always on universal media box hub that ran silent for 20 years. Microsoft actually made a big deal about saying that then design language was so it would look at home in a media centre.
That vision died almost a year ago. Now it's back to being an Xbox: gaming machine that also does media well.
I don't agree. The updates are only making it a better allways on universal media box hub.