Status: CM13 Source code released 
  Update 3 (19th Oct. 2015): CM13 source code is out. Unofficial ports should be coming in hot now. 
  Update 2 (15th Oct. 2015): We’re exactly in the middle of October but there’s no news from the CyanogenMod team for the release of CM13 yet. Seems like we’ll have to wait a little more now. But we’re still faithful that CM13 will happen in October only. 
  Update (5th Oct. 2015): Android 6.0 Marshmallow source code is being merged to AOSP today. Expect CM13 to come in a couple of weeks now.

CyanogenMod 13 will be the next version of the world’s most popular custom ROM for Android, and it will be based on Android version 6.0 Marshmallow that is to officially release on Sept. 29th by Google.

CyanogenMod 13 will also be called CM13, like the previous versions of the ROM have been. It’ll be available once Google releases the source code for Android 6.0 Marshmallow into AOSP (Android Open Source Project).

Google will be releasing the Marshmallow update to some of the Nexus devices on launch, but for devices other than Nexuses, it may take time until the update is officially available for them.

Also, not all Android devices will be getting Marshmallow update, matter fact, very few percentage of them will get the update officially before the end of 2015. There are many reasons for this, but the most clear is lack of support from manufacturers and carriers.

Thanks to custom ROMs like CM13, you may not have to wait long before you could get a taste of Marshmallow update on your Android device. CyanogenMod officially supports a lot of devices, and even the ones that it doesn’t officially support, also get the latest version of the ROM (unofficially) by the love of community users.

If your Android device is old, chances are you’ll not get the Marshmallow update officially on your device. But that doesn’t mean you can’t have it. By means of CM13 and other similar ROMs, that will release once Android 6.0 source code is in the AOSP, you’ll be able to install Android Marshmallow on your old Android device.

Since Android 6.0 is officially releasing on 29th September, we expect CM13 to be available by mid-October 2015.

Happy Androiding!