Given the show's long history and continued popularity, we wouldn't be shocked if MTV announced its renewal of "The Challenge" sooner rather than later.
It's feasible to speculate about the 38th season's release date based on the release dates of prior seasons, but it's impossible to know for sure.
you can expect to hear more about it in the near future, and it should launch sometime in the spring or early summer of 23 July 2022, assuming that there are no major delays.
Reddit discussion suggests that production won't begin until March, so a later premiere date is also plausible.
As far as a reality competition show's "cast" is concerned, there's just one person who can be considered almost certain to return for Season 38.