Kalki-das

In short Kalki is the tenth avatar of Vishnu who starts the Satyayug after He dies. No Satyayug started after Mohd died. As for Jesus, he is in the Bhavishya Purana as Ishputra the Son of God. I believe dat Jesus was not a normal person but it would not be right to consider Mohd as Kalki. Kalki is an avatar i.e. He is God Himself. Mohd was, according to Islam just a prophet.