Can he be voted out?
This late? No idea.
Yes, in November. This is a Dem seat. Always was, always will be. This guy is an historic anomaly brought on by the corruption of their former congressman. He has zero chance of holding that seat.
Cao will almost certainly be replaced by a Democrat in the next Congress.
He only won the seat because the incumbent, William ("Cold Cash") Jefferson (D), had an appointment at the pokey. And, in the wake of Katrina, the district's demographics were temporarily altered.
You can count on Cao disappearing into the electoral mists and another corrupt black Congressman (or woman) being elected in his stead.