Takuan said he might not be able to walk. I imagine he'll make a recovery, he still has Kojiro to fight, maybe a few others depending on how much of the rumours around Musashi's life Vagabond goes into. For example, Musashi was supposed to have fought with that Gonnosuke guy (who formed his own school for the wooden staff), the one who followed Kojiro and Ittosai around for a while. I guess we'll have to wait and see...