Please install PanicMode browser extension for Chrome (https://chrome.google.com/webstore/detail/panic-mode/lamdafc...) and try to surf the web for a day. You will know what I mean as soon as you go through this experiment.
Disclaimer: I am the author of this extension. I wrote the extension for personal reasons and it is very simplistic in nature. If you turn PanicMode on it will replace every outgoing http:// url with https://. It does nothing else besides that and unlike HTTPS Everywhere it has no exceptions list or special handling of the top 100 sites, etc. The site you are visiting should either support https:// or it will blow up in your face, which is exactly what happens 90% of the time.
Edit: Besides just because Firefox is seeing more HTTPS traffic means nothing if all the traffic comes from Facebook, Google, YouTube and a few others. Yes, there is more traffic and yes it is encrypted but does it really say anything about the state of the web? Someone needs to put this data out to make it clear.