They would be the successors of Xbox One X and Xbox One S.
According to information from Brad Sams, Thurrott's website, Microsoft is preparing hardware aimed at different audiences for your site. Xbox next generation known by code name Scarlett.
Speaking more specifically, he mentions that the company works on a couple of Pro and Arcade models that are codenamed Anaconda and Lockhart, respectively.
The Scarlett Anaconda would be the Pro model and would be the successor to Xbox One X with more power, while Scarlett Lockhart would be the Arcade and direct successor to Xbox One S.
In addition, Sams says that Microsoft also works on Anthem which will be a version of Xbox One S that will work specifically with XCloud, the new platform streaming of the company, and this, of course, will be more affordable. He even points out that there will also be an Anaconda model that will work with this service in the cloud.
Finally, it is said that AMD will be the maker of chips for the next-generation console, apparently based on AMD Zen 2 microarchitecture.
The report mentions other plans and products of the company, but for now we should take all this as a mere rumor and wait for more accurate information. Meanwhile, the possibility of launching Pro and Arcade models that would come to please different classes of consumers and that apparently worked in the current generation, seems feasible.