Assuming you have RVM installed, don't wait:
rvm install 1.9.2and you will be up to date. I wrote a small utility app to browse MongoDB data we use for text mining for my customer this morning and I used Rails 2.3.8 and hopefully that will be the last time I start a new project < version 3.0. My excuse for not using version 3.0 was that I wrote and deployed the app in less than an hour, and I am just not up to speed on Rails 3 yet. That will change!
gem install rails