AFAICT, what's on the table is *toll only* lanes on US 69 from 151st Street north to I-435. There does not appear to be any discount for HOVs, nor is there any indication that said toll lanes would be operated by any organization other than KDOT or KTA.
AIUI, toll lanes would have to have the support of the local governments involved, and I'd suspect if significant opposition to toll lanes of US 69 develops, the toll lane proposal will get shot down. Toll lanes were floated for the western leg of the South Lawrence Trafficway, but it became quickly clear that there was opposition to it.