Hello. I saw that Sai got a new rank in the Retsu no Sho which was initially dubbed as Tokubetsu Jonin but was corrected afterwards as the rank is a different one. Seelentau was so kind to tell me the kanji and loose translation of it. The kanji are 柱部, which is read "chūbu" and could mean "Support Section". I presume that he is once again part of a group, just compare the name with Anbu, the last kanji matches. A theory that I have is that the Anbu Corps was renamed, as the world becomes peaceful and assassination is no longer needed, hence the Anbu are instead a "supporting" faction now. However, that's just speculation.
I found nothing by myself about it, so I ask the community if anyone found anything about it. Even better, if somebody here has seen the movie, could you tell us if Sai's rank got mentioned in it in any way?
If there's no information, a new article about it is not valid. However, we could still mention in Sai's infobox that he is a "chūbu", so we use the romaization of the japanese name just as we do it with jonin and chunin and so on.
Considering that now the Shinobi World is perhaps truly are in peacefully times they may have dumbed down the violence/hostility of the ANBU. When they were once hardcore all the way, now I believe they're softcore to hardcore now considering that day and age of the Shinobi World. All and all that's a good ranking for Sai considering who he is and all.
I found some speculations (like Sai now being both a chūnin and an Anbu, hence "chūbu"), but nothing that explains the rank. Nevertheless, I think we should put it into his infobox, as we at least know how his rank is called.