Android screen mirroring to Chromecast “very soon” and plans as such are been working around with Google which will allow users to stream their phone screen to a television set seamlessly.
It was found in Android 4.4.1 code by Koushik Dutta (Co-founder of CyanogenMod). Even then, there is noting clear as to when Google plans to release the feature, but small code pieces are usually meant to be as an indication of features to come in the future.
Currently Chromecast is available on the Google Play Store for $35 which allows mirroring from a Chrome browser tab on laptop or desktop to a television, but so far on Android devices it has been locked down to supported apps like Netflix, HBO Go and many others.