I'm optimistic that we'll see pretty widespread support, maybe 3 of the 4 major engines, by the end of 2016, with the 4th following shortly. The face-to-face meetings have gone extremely well, and all browsers are pretty motivated to ship quickly.

The Web Component polyfills and Polymer will also be updated to support the new versions of the standards.

I think so. At this point all browsers are on board with shipping Custom Elements and Shadow DOM and Template has already shipped everywhere. The holdout is HTML Imports and the Chrome team is currently working on a revision to that spec to build it on top of the ES2015 module loader so it's not contentious (https://github.com/w3c/webcomponents/blob/gh-pages/proposals...). But HTML Imports is not a requirement for Web Components, the big win is Custom Elements, so seeing everyone get on board with that is awesome :)