ZBrush 4R8 is still in development. Pixologic does not give release dates because the focus is more on quality than calendar.
When it does come out, you’ll be hard pressed to miss it. There will be announcements via Pixologic.com, ZBC, G+, Twitter, Facebook and ZBlog. You can also subscribe to the news RSS feed at https://support.pixologic.com, which is only updated when it’s something major.
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