The successor to Research Unix was Plan 9 from Bell Labs

Plan 9 from Bell Labs is a successor to Research Unix that rethought the core concepts of Unix for the 1990s. It focused on networking and treated everything as a file. While it had some good bits, like its simplicity and functionality, it ultimately flopped and couldn't replace Unix due to its incompatibility and lack of certain features. However, there is potential for bringing some Unix tools to Plan 9 through microVMs.