Mobile-First Indexing - This will change the way that your website gets ranked in the search engine results pages (SERPs). There are a few things you need to know about the mobile-first index so that you can optimize your website accordingly and avoid being hit hard by Google search rankings adjustments.
It's better to be save than sorry in this instance. Start optimizing your website to be mobile responsive before the new years, so you can be ready to have mobile traffic to your site. Over time, you'll thank yourself for making these changes to your site on time.