It's possible to have multiple versions of Android Studio installed simultaneously. When we offer canary builds (or even beta builds) of the next version of the IDE, you may want to install the new version without replacing your existing stable install.
Android Studio stores its settings in version specific folders; the exact locations depend on the operating system (and the versions of the IDE), but for example, if you have both Android Studio 1.5.1 and Android Studio 2.0 Preview 1 installed, these will consult settings in
Therefore, once you've installed the two versions, you can use them, even side by side, and they should not interfere with each other. (Note however that newer versions of the may change some of the configuration data in your projects (such as code style settings in .idea).
Note that on OSX, you typically install by just dragging the "Android Studio" app from the DMG folder to your Applications folder. Doing so will cause it to replace the previous install with the new install. To avoid this, rename your existing app first, for example from "Android Studio" to "Android Studio 1.5".
Once you are done with an older version, you can delete the settings folder for that version. This can free up a significant amount of disk space; particularly the index caches.