If Kizaru was done for the arc oda would’ve had him shown unconscious from a double spread. Odas leaving the door open for Kizaru and Luffy getting up at the same time for round 2 for a reason.
Which if you think about it makes sense, if the Luffy vs Kizaru fight was still ongoing while at the same time Kuma's flashback was happening, many readers wouldn't really care about the flashback and would want to go back to the present just to see the Luffy vs Kizaru fight.
Either way once Kuma's flashback is over, both Luffy and Kizaru will get back up and we will have a round 2.