Google already started to working on the mobile-first indexing process, which means 70% of sites already shifted to the mobile-first indexing. the remaining 30% of sites only need to be pending. According to Google, coming September onwards we’ll be shifting to the mobile-first indexing for all our websites. I hope this is a great chance to see how the web has grown from the desktop to mobile.
source: http://bit.ly/2TF0wq7