Google recently announced that it would give a slight ranking boost to HTTPS websites, but a recent report from Search Metrics indicates otherwise.
Marcus Tober of Search Metrics compared rankings from unsecure sites with those of secure sites, and found no difference between the two data sets.
It may be too early to tell if securing your site will improve rankings, but so far, it does not seem so. A larger sample size may also be needed.
It is unclear how long it will be until secure sites see any ranking boost, or if they every will experience enough of a boost to be noticeable.
It was widely believed that the new secure website ranking factor was created in an effort to create a safer, more secure Web. This may still be Google’s intentions, but for now, migrating your site from HTTP to HTTPS will only benefit users, not your SEO (at least according to Search Metrics).
Site owners should continue to keep their ears open, as Google is prone to announce unexpected updates. If anything is certain, it is that Google is fairly unpredictable.