Originally Posted by Phoenixtinct

This is incorrect. It has been announced that with the merging of the programs both AA- and US-operated flights will be eligible for SWU upgrades. Whether that means it will include codeshares, i. e. AA-operated booked as US codeshare and vice versa (US-operated under AA codeshare) is unclear. The exact language is:

use systemwide upgrades on flights marketed and operated by American and US Airways