If newer versions of Rubygame, SDL or any of the other libraries Rubygame relies on are released, you'll need to install newer versions of those libraries in order to get the new features. To do this, you can download the libraries directly from the following websites.
Some of these may require you to compile the libraries yourself from source code. If that's the case, you'll also need a compiler such as Microsoft Visual C++ Express Edition. The libraries are distributed with project files for compiling the libraries with Visual C++.