The following was taken directly from Micheal Bispings official website:

The rematch betwen Hamil and I was being planned for Nov 27 in New Jersey. Unfortuntely Hamil is unable to fight as he is having knee surgery. I am dissapointed as I was really looking forward to fighting him again. That said, myself having a torn posterier cruciate ligament in each of my knees for my last 3 fights I can understand why he’s having it.

Wishing you a speedy recovery matt and hopefully we can “get it on” soon. On a side note it gives my big toe a chance to heal as I stubbed it on the way o the octagon.