Nikon announced the release of EN-EL18"c" battery on the 13th of this month. It replaces EN-EL18"b" that has been sold out this April:
http://www.nikon-image.com/products/info/2018/0706.htmlThe texts of the linked page is all Japanese, but the announcement in other languages should be made shortly.
The "b" version has been discontinued and sold out this April, due to the change of its production process. According to the article of Impress-Watch...
https://dc.watch.impress.co.jp/docs/news/1131819.html...the "c" version is identical to the "b" version.