This fight needs to happen. Either Cyborg gets the KO, or if Ronda gets it to the ground (which I believe she could) she may possibly pull off a submission, which still won't be easy as Cyborg is a legit grappler as well. Until then, the safe bet is to say Cyborg beating Rousey to a bloody mess.
They say Ronda has a great jab, but it's going to take more than just a jab to completely neutralize a killing machine like Cyborg on the feet. Ronda might be biting off more than she can chew, but we'll never know until they finally get this fight down.