There is only a single android plugin, and that is maintained in AOSP.
- In Android Studio, we ship IJ 13.x + latest version of the Android plugin.
- IntelliJ 13.x is in stable mode, so they use a relatively old (very old if you are looking for Gradle support) version of the Android plugin. I believe Jetbrains only cherry picks bug fixes into the version they ship with 13.x
- IntelliJ 14.x EAP channel could possibly use a more recent version of the Android plugin.
The specific version of android plugin shipped as part of IntelliJ is completely under Jetbrains' control. They decide when to merge our changes. Typically, during EAP phase, they used to pick up changes every two weeks, but as they near their stable release dates, they only pick up bug fixes.