Before we start speculating about the future of Microsoft's Xbox gaming system, it's important to note that none of the information that you may read down below has been officially confirmed by Microsoft or its subsidiaries. While some of those rumors may (or may not) turn out the be true down the line, we still know next to nothing about the long-rumored Xbox One next-gen successor(s).
According to Windows Central senior editor Jez Corden (whose reputation is spotty, at best), "the next-gen Xbox/dev kit is codenamed "Anaconda," in-keeping with the reptile theme." As a reminder, the dev kit for Microsoft’s Xbox One X (also known as Xbox Scorpio) was codenamed Chuckwalla, while the original Xbox One’s dev kit was codenamed Durango. Please remember that it’s just a codename that only refers to the name of the console’s development kit, and not the console’s actual name.
The development kits are software development tools for hardware that are designed specifically for game development purposes that are usually send to gaming studios to allow them give their valuable feedback. Considering that some Japanese developers (like Final Fantasy XV studio Luminous Productions) are already testing PS5's dev kits, it shouldn’t be surprising that Microsoft is trying to keep up with the arguably more successful rival (when it comes to this generation of consoles).
During E3 2018, Xbox boss Phil Spencer confirmed that Microsoft is working on an Xbox One successor that has been reportedly condemned Xbox Scarlett. Since then, several reports have been suggesting that Xbox Scarlett is in fact the name Microsoft’s next-gen project that includes a family of devices broken into several tiers. There’s no way of knowing how accurate this is, so take it with a pinch of salt.