The most likely out of the options you have given us is Bill Gates at CES would announce the internal HD-DVD drive into the Xbox 360 being built another manufacturer. This is still a probably a 20% chance and the topic was probably extensively researched by MS to see if it can provide positive aspects for the company.
I personally do not believe they will add Blu-Ray to the 360 internally, or even in an external accessory.
Microsoft it always aggresive! Remember from the Simpsons? "I don't get rich by writing cheques Mr. Simpson, Mwuahahahaha"
They probably won't buy another studio since it is already the #1 platform to make games on for third-parties. They already have huge support from developers.
They'll most likely act like the format war never existed or claim they didn't support them too much or some foolish PR movement.
And lastly, I think they are still selling 360 at loss? A while ago they were also selling at a loss, not sure if it got any cheaper to manufacture. I honostly can't answer that. Just my assumption.
EDIT: madskillz cleared the profit/loss thing. The 360 is being sold at a profit margin
