The first 1.0 release candidate is on PyPI now: https://pypi.org/project/rasterio/1.0rc1/. I've scheduled another for Friday, which will remove a deprecated module and deprecated methods of dataset classes. I feel great about reaching this goal. I hope you'll give the release candidate a try!
We will not be having an extended release candidate phase. A final 1.0 release could come as soon as next week. Until then, I expect to be mostly busy with documentation, blog post and announcement drafting, and project wrap-up.