It's unclear which changes will make it into the general release November update, but Insiders are still getting features early. Microsoft has just published Build 10576, which contains a few interesting additions, but one that stands out. Microsoft Edge will be able to cast (unprotected) content to any Miracast and DLNA device on your network. This could be something like a WDTV Live or an Amazon Fire TV. It might even work with the PlayStation 3, Xbox 360, and Xbox One, but that's just speculation from a quick Google search.
So basically, it works with YouTube, Facebook, Pandora, and other sources. It will not work with Netflix or Hulu, which use EME, though.
There are quite a few Known Issues with this build, though. Volume gets ducked when the system gets a notification, some devices will bluescreen if their display resolution is odd, a few codecs are still missing (although that last issue was around for a couple of builds).
If I were to guess, I would expect that these features are targeted for Threshold 2 in November. I doubt that we have seen anything scheduled for Redstone 1 yet, but I could be wrong.