The main reason I also think the original Xbox ONE will come down in price, is simply because when the Scorpio comes out, Microsoft won't be able to justify selling the previous console at such a high price (even though it is relatively low)
People aren't going to buy an Xbox ONE when they can buy a Scorpio for not a great deal more, so if Microsoft do want to keep selling the Xbox ONE as well, they are going to have to offer an incentive, and the main thing they'll look at ill be dropping the price I would have thought.