Moving your site to HTTPS has its own advantages & disadvantages from a SEO point of view. There are many challenges associated with moving to HTTPS. It involves a series of 301 redirects. These redirects are usually associated with loss of link equity resulting in loss of rankings. Google is also emphasizing on switching to HTTPS & data has to be evaluated to see if the win/loss gain from switching.
Another problem is the loss of referral data. Referral data plays an imp role in finding who is the referrer, what kind of site & others. No referral data is sent when traffic is refereed from a HTTPS to non HTTP site.
Meta referrer tag can be used to send data in such situations. Traffic remains encrypted & HTTPS can also be used.