$550-600. I might. If there is a Halo themed one I will. It also depends on how well it incorporates VR and if Halo supports VR in the future.
This. I will but because if I remember correctly to you can sell your Xbox one for a Xbox S or Scorpio for 200$ off.
I don't believe they have hammered out the exact details, as this article mentions it will likely be up to the agreement retailers make with Microsoft.
Also, from the same article, which I'm not sure how accurate this is admittedly, as it seems to make a few contradictions throughout the article, more specifically in terms of if this is the last console that Microsoft will release, but it is an interesting read.
Link