I still find it interesting Bitmain has put 'Coming Soon' on their R4 product page but they haven't come out with any news about it yet. Same for the clock-router LTC miner that they have, the page for that showed up 2-3 weeks ago but there's been no news about it whatsoever besides the product page.
They may have been quiet, but they were not cost effective. S9s provided a lot more hashing for your dollar than the R4s did.