We've been recommending to our clients to move to https for some time now as Google in 2016 made announced that beginning in January 2017, they are going to mark all the non-secure websites in their Chrome browser.
What that meant was Google implemented a feature in Chrome where a warning would display on http sites where there was an entry field of any kind on the page.
The final step is that Google will make that message much more noticeable and will send a clear signal to the user: you risk exposing your personal data on this site, use at your own risk.
The likely effect of this will be negative and turn potential customer away.
Apparently Google is not stopping there, in the several locations in the US they have been testing a way to mark non-secure website in the Google Search results page. This will have a much bigger impact as the likely effort will be potential customers won't even visit your site!
So take action now to migrate your site to https.