Good question, however if it is those 2, then hamara can't be summon yet since Hinata and the other hyuga are being zetsulized and kimi is gone since edo tensei ended-I think. Although I'm hoping the brother is shown some way, maybe the sage's plan involves retrieving Hamara or summoning by a similar method that he was. Maybe the sacred treasures involve Hamura in some way, or there are other treasures that have his chakra connected to them.