Sane has resumed training at City after missing out on an August move to Bayern due to a knee injury suffered in the Community Shield.
"Now you have to see how he will come back after his injury. According to my information he is now starting to train again but is not yet back in team training."
Hainer then declared that Bayern are looking to win the Champions League in the next three seasons, suggesting Sane could be a part of that.
He continued: "However, it can be assumed that we will prepare the team not only for the next season but for the future I don't just mean the German championship, because we want to win the Champions League again. After all, we have the final at home in 2022 and we want to win there at the latest but I don't mind either."