rvm adds ruby 1.9.3-rc1 into their set (ruby developer community announced it on last Saturday 24th Sep 2011). I tried this on a Mac. Should be the same on linux as well.
Before installing ruby 1.9.3-rc1 , you might want to check out what is being deprecated and what is being added in future versions of ruby. There is a blog post on rubyinside about this.
rvm install 1.9.3-rc1
rvm use 1.9.2-p290
rvm gemset export 192.gems
rvm use 1.9.3-rc1
rvm gemset import 192
rvm —default 1.9.3-rc1
Change the appropriate .rvmrc files in your projects to use the new and improved ruby.
Sairam's Blog 