Why should you run your site on HTTPS? Well, to protect your users information, so it’s a good idea. But do you, or plan to, or even need to?
Beginning in January 2017 Google Chrome browser will mark HTTP sites that transmit passwords or credit cards as non-secure, as part of a long-term plan to eventually mark all HTTP sites as non-secure.
This could lead to SEO issues for you as non-HTTPS sites are downgraded in results of Google, so something to start thinking about I’m afraid, especially if you plan to go to HTTPS and have 3rd party content, Ads, etc (which might not be using HTTPS).
The Google announcement can be read online or if you want a more in-depth video from the same author as the Google announcement (Emily Schechter, Chrome Security Team), check this out video:
There are many HTTPS related plugins available on the WordPress repository.