Hi @igor,
At present, while we make major releases -- as well as most minor and patch releases -- of R available in RStudio Cloud, we don't currently make development releases available.
That said, if there's a specific use case you have in mind that would benefit from having a development version of R available, we'd love to hear about it. While we don't have plans to do this today, it may be something we consider in the future.
Thanks!
Mel