To no ones surprise, Google announced mobile-friendly is becoming a ranking factor in the mobile search results in the near future. Google said it will happen on April 21, 2015 - first time they actually pre-announced an algorithm release with a specific date.
We knew this was coming because they have been experimenting with mobile friendly factors prior, they have been pushing mobile friendly labels in the search results, they have been releasing a testing tool, usability reports and much more around encouraging webmasters to go mobile-friendly.
Starting April 21, we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.
Will it be on April 21st? John Mueller of Google said on a Google+ hangout that he is not 100% sure, but he said it won't be before the 21st, so webmasters have time to prepare. In the hangout, starting at 25 seconds in, he discusses this and gives a presentation. Here are screen shots of the slides in his presentation and the video:
There is a lot of webmaster discussion around this and if anything, it is now time to go mobile-friendly. Really.