In theory this is a smart move by Google.
The thinking behind it is that HTTPS sites are more likely to be genuine, legitimate websites and therefore be better quality results for user’s searches. There are arguments against it, mainly that simply having a secure certificate for your site doesn’t automatically make it legitimate. There’s also some scepticism about Google’s suggestion that HTTPS should be everywhere by default.
Another big issue could be that this change in approach could lead to inexperienced website owners setting up their secure certificates when they don’t really know how to. This may cause issues with their sites losing rankings in the search engines and might even lead to people breaking their websites completely. My main concern though is that HTTPS sites are robbing us of valuable analytics data!