We had been participating in JSR-333 several years ago until activity on it stopped. Basically, it was hung up on the reference implementation, and the Jackrabbit community had not really expressed an interest (since most of their activity had moved to Jackrabbit Oak). None of the other implementations implement all of the optional parts of the JSR-283 spec (including Jackrabbit Oak), so lack of a reference implementation for JSR-333 was the nail in the coffin.
How will this affect ModeShape? Basically, not at all. We've already implemented the few API changes we hoped to see added in JSR-333 via our custom API extensions to the standard interfaces and our extensions to JCR-SQL2. So, ModeShape will continue to be implement the JSR-283 specification.