The update is only intended for rankings on mobile devices and will affect search results in all languages, and apply to individual pages, not necessarily whole websites. Don’t panic just yet! Google wants to reassure marketers that mobile-friendly isn’t the only variable considered in their algorithm, and that pages with high quality content that is well-matched for a search query could still rank well even if it’s not mobile-friendly. As always with Google updates, if you’re providing quality content with good intent for the user, you will not be “punished…” much.
CNET makes the point that more and more people are surfing and purchasing from their mobile devices, (around 60%). Therefore, if you don’t have a properly formatted and optimized mobile site by now, you could really be hurting your chances for conversions and customers.
In short, start working toward making your site’s pages mobile-friendly ASAP, or start losing ranking in mobile searches.
If you’re not sure whether your site’s pages are mobile-friendly you can use the Mobile-Friendly Test to check each page, or use Mobile Usability report in Webmaster Tools to test your entire site.