Google’s Gary Illyes has stated that a substantial number of sites will migrate to mobile first index in the next month & half. He also announced Google’s upcoming plans for mobile-first index.
The last official announcement from Google about mobile-first indexing was during last summer, when Google’s John Mueller stated it was rolled out for individual sites which were ready. They initially planned to ensure that all sites migrated to mobile-first index by the start of 2018. However, the goal hasn’t been met.
Google has also stated that it won’t announce when migration to mobile-first index is complete. But after Illyes’s keynote at Pubcoin, it has become clear that the new index might never be rolled out for all sites.
At present, only a handful of sites have been added to mobile-first index. This is not expected to make any impact on traffic. Knowledgeable site owners can verify whether their site has been added to mobile-first index by checking server logs to find out what is crawling the site most of the time. If Googlebot mobile is doing a major part of the crawling, then there are high chances that your site is on the mobile-first index.
You cannot determine if your site has migrated to this new index without manually verifying server logs. This is because Google isn’t notifying webmasters individually. In case you are ready for mobile-first indexing, then your site will be selected in the weeks to come.