New tags are given an "x-" prefix by default, so that's not an issue. That said, you can opt out of the prefixing by changing the namespace string - but even if you remove it and there is a tag created down the road of that name, it doesn't mean your stuff is sure to break.
It looks like you have to prefix the tag names you register with an x- in your html.
The prefix is added as a default, but can be changed or even removed - it's up to you, the developer.