What’s a man to do when he announces he is retiring his acting name? Why, take up directing of course. What a silly question. Undoubtedly, Sonny Chiba is a name synonymous with Japanese cinema and it is good news to hear that although he has retired from acting in name only he is still continuing to contribute to the art form. Or, should we be concerned that the man has so many alter-egos?
He will begin directing movies under the name of Rindo Wachinaga (和千永倫道). I don't know what the significance of that name is, to be honest. Word is he already has two films on the go. The first one, titled Bushido, depicts the life of Nitobe Inazo, the author of "Bushido: The Soul of Japan", which was a book about the study of the way of the samurai. The other movie is called New Key Hunter, that will be based on the television action series "Key Hunter" (1968-1973) that Chiba starred in with the late Tetsuro Tamba. I’ve included the trailer and all it’s funkiness at the bottom.

I like that Sonny Chiba has multiple identities now. One was not enough to contain the greatness. Now, does this apply in English? I heard it was Shinichi Chiba (in Japanese characters) that was being retired. You can't possibly improve on Sonny Chiba, and if he's retiring it I claim it for any eventual male offspring of mine.
According to the couple Japanese sources I just read, yeah, it is Shinichi Chiba that is being retired. His acting name will permanently be JJ Sonny Chiba, and directing name is as you say.
According to this goo.ne.jp article, Wachinaga is a variation on his mother's maiden name, and Rindo takes the meaning of "A road of people"/"People's road" or maybe rather "The way of people".
He wants to graduate the Shinichi Chiba name by the end of the year.