It will rank better, sure, but I cannot believe it would rank significantly better. Two exactly SEO matched sites with the exact same amount of unique visits per month, then maybe there would be a small advantage if one had SSL implemented.
However, to make it fair, I admit I have added SSL encryption to one of my sites, but that was mostly because I wanted to take payments via the site, so needed the certificate anyways.
HTTPS is becoming a requirement for any webmaster serious about web business. Even if you don't do it for SEO, do it for your clients. I have already implemented it for my sites that accept payments. Ensuring your login pages are HTTPS is a good practice too.
I do agree with that point HTTPS is necessary and mandatory practice for accepting payments, but for a normal blog, why should someone invest more dimes ??? What about other search engines, will they able to crawl that easily like were doing before.
Well, I quite disagree with the topics. I don't think that having HTTPS is gives you more better ranking than old HTTP. Currently I have a blog which have old HTTP but still it occupy a good rank and space in search engine. I think having a HTTPS is just increase the trust level of readers if you dealing with online payments and relatively other things.