So Google have told us by going HTTPS/SSL will provide the site with a ranking boost (but only a minor one). Google have mentioned that this factor is only very small and high quality content is still the key and plays a much larger proportion in the final decision. They say that is has "fewer than 1% of global queries", but they may decide to increase the factor to encourage websites to go the secure way. They wont increase it just yet as they will give webmasters time to adopt this change.
Matt Cutts (Head of Search Spam) did mention at SMX West that he would love to see SSL being a ranking factor!
Full Article: http://googlewebmastercentral.blogspot.co.uk/2014/08/https-as-ranking-signal.html
This change was announced on August 6th 2014.