One thing that may show up in Redstone 5 is a new Windows search experience. Microsoft has been working on this new UI for some time, and it is likely part of Microsoft’s larger effort of moving Cortana into the Action Center in Windows 10. A lot of this work has already been done in Redstone 4, so it’s not too hard to imagine that more will show up in Redstone 5.
We’ve already seen what this new search UI looks like thanks to a registry edit that enables it in Redstone 4. Perhaps we’ll see this new UI evolve throughout Redstone 5 as Microsoft makes its intentions more clear.
There are many other features in the plans for Redstone 5 from what I’m told, including more improvements to Microsoft Edge, Fluent Design, My People, and the Action Center. We may also see Windows Core OS make an official debut with the Andromeda device, which is rumored to launch this fall.