Qt Creator 4.2.1 is now available for download and comes in as a bug fix update. This release has also been made available concurrently with the release of Qt 5.8. It comes with optimizations for some of the new features available in the new framework release.
You can get a copy of Qt Creator 4.2.1 from the official download page here. Those with commercial licenses can get it from the Qt account portal while those using the Qt maintenance tool can use it to update their current versions.