Sony Australia officially confirmed this:
“The Sony SAL135F18Z camera lens has been discontinued and will no longer be in production as of this week. The website may still show that it is in back-order, but the information on the website will be updated anytime from now.”
I don’t know if that means that Sony will no more sell that lens in Australia or if a new version II is about to be released. What our sources told us is that Sony will update some of the current A-mount lenses to improve the autofocus performance.