During yesterday's Windows Insider Webcast, the Windows Insider team mentioned the initial Redstone 4 Windows 10 bug bash will be coming up on February 2nd (via Neowin.) This is the first of what may be many Bug Bashes for this development cycle, perhaps also being one of the first signals that development of new features in Redstone 4 may be winding down soon.
It's not certain at what time the Bug Bash will kick off, or at what time it will end, but these Bug Bash events usually last a little over a week. You can expect for Microsoft to share the timeline, and the specifics of what bugs they are looking for soon, but for now it's best to keep those bug reports coming via the Feedback Hub.
Update: Microsoft officially announced the Bug Bash in today's blog post for Windows 10 Insider Preview build 17083. It will run from February 2nd until February 11th. There will also be a Bug Bash webcast on February 6th on Mixer.
— Jen Gentleman 🌺 (@JenMsft) January 23, 2018
Bug Bashes also usually come with quests in the Feedback Hub, putting Windows Insiders in charge of trying out specific Windows features and reporting back to the Insider team on how everything works. We last saw a Bug Bash for Redstone 3, and the Fall Creators Update back July of last year.
Microsoft will also be holding a special bug bash webcast on Mixer, giving Windows Insiders a chance to interact with members of the Windows 10 team. You can expect more details soon, maybe in an upcoming build blog post, so be sure to keep tuned for more in the days ahead.