Latest USAF plan is to ditch previous KC-X, KC-Y and KC-Z programs and go for 179 x KC-46A on order - then 75 x possibly competed KC-46A / something else - then Next Generation Air-refueling System (NGAS) - which seems the same to me as KC-X, KC-Y and KC-Z in all but name - just changing the planned numbers of each!
USAF Shakes Up Its Plan for Tankers: Fewer ‘Traditional’ Refuelers, Focus on Stealth Future | Air & Space Forces Magazine (airandspaceforces.com)