Android 4.3 system dump for the T-Mobile Samsung Galaxy S4 (M919) has been leaked online. The system dump is now available for download, this is a system dump so you cannot flash it but some skilled developers can of course make it into a flashable zip.
Here is the download link for the Android 4.3 System Dump for T-Mobile Samsung Galaxy S4. The build number is JSS15J.M919UVUEMI9. Let’s hope a Android 4.3 flashable zip for the T-Mobile Galaxy S4 is available soon.