Back in July, Google began testing a new feature that would allow users to enable a Wi-Fi-only mode for Maps, which would help those with limited or expensive data plans avoid overages. Well apparently the tests went well, as Google has started rolling out the addition to Google Maps on Android.
Wi-Fi-only mode can be toggled on in settings and will limit the app to only working with your saved offline areas unless you're connected over Wi-Fi, while the rest of your device operates as normal. Maps for Android is also picking up SD card support, allowing you to download those offline maps without eating up your local storage.
The new updates have begun rolling out to Android users now, but as with most Google updates, it will likely take a couple weeks before everyone has it on their device.