Klemen Kloboves from Google said "beginning in May, we’ll start rolling out an update to mobile search results that increases the effect of the ranking signal to help our users find even more pages that are relevant and mobile-friendly."
He said two more things:
(1) "If you've already made your site mobile-friendly, you will not be impacted by this update." Will you not benefit more from this update if they are boosting the signal? Or maybe the change will only have a negative impact on pages that are not mobile friendly?
(2) "The intent of the search query is still a very strong signal - so even if a page with high quality content is not mobile-friendly, it could still rank well if it has great, relevant content." So non-mobile friendly pages can and will still rank, if the query deserves it.
We've covered the first mobile friendly update exhaustively and you can catch up on all of that over here if you have the time.
In short, test your pages to make sure they are mobile friendly using this tool.
The first mobile friendly update was not a "mobilegeddon" as many expected it would be. This one will have even less of an impact than the first, so this one should not be a geddon at all.
Gary Illyes even said that on Google+, "was there anything catastrophic about the first mobile friendly update? If not, then I'd prefer ditching that name."
So no need to panic, just go mobile friendly already if you are not.