It was never a given that the KC-46 would fill the KC-Y requirement as well as the initial KC-X requirement.
The KC-46 has lots of additional stuff for "'special requirements" that aren't needed by the entire tanker fleet.
US TRANSCOM has been looking at multiple options for about a year now - including Contractor Owned Contractor Operated.
https://crsreports.congress.gov/product/pdf/IN/IN11537
The problem for Airbus is going to be the conversion rate they can achieve - which is currently 5 aircraft per year.
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