Got replies from KYTC staff. Yes, the Parkway will be extended to US 23. Signage is coming, and once there's evidence of it I'll update the map. As for KY 80, no one was sure how that would be dealt with yet, but the District 12 person said he would investigate. Past the junction with 23 south of Prestonsburg, there's only a short segment (less than 7 miles) of 80 that's not concurrent with at least one other route.
The US 460 project is proceeding and the person I spoke with was hopeful it would be complete by the end of the year. He also confirmed that the former routing would be Alternate 460, and implied that Virginia would be using that designation as well.