I thought the ending serene and "felt" appropriate despite lacking that closure which comes with an epilogue. Kneeling on that soft sand as the waters lap the shrinking island, tears streaming down his face... it's like, a long pent up sigh of relief and gratitude, finally let out.
I've seen these sort of abrupt endings before in older media, like kung fu flicks - the journey was the thing. You had to have your final showdown, of course, but now that it's done... it's done. At any rate, most everyone died along the way anyway.
Musashi... I got the impression he could have ended Jubei whenever and however he wanted if he was serious from the beginning, especially when he mentioned how Kojirou struggled and expended his energy just finding the right footing. On a minor note... I thought Musashi's boatman was going to be the penultimate death in the series, but nope, old guy had enough sense to push off. I suppose old man Yagyuu was the other guy that probably would have beaten Jubei straight up.
Well, a fun ride while it lasted, and it's a treat to read these volume by volume. Thanks and see you down the road.