Since Microsoft has done away with software development for Nokia X series of devices there is no possibility for any new OS / Firmware coming officially for Nokia X series. Anyways, there are some stable custom ROMs like Lewa OS 5.1 that are still available and you can download and flash them to your Nokia X, Nokia X2 and Nokia XL. But at your own risk, as it terminates warranty and can also cause harm to your device if not done properly.
Lovi OS is an AOSP and CynaogenMod 11 (Android KitKat 4.4.4) based custom ROM for Nokia X, X2 and XL. It is supported by TFK Project and latest ROM from Lovi is Lovi OS 2.0, that is now available for Nokia X family of devices. Here we found a video on YouTube that demos the new Lovi OS 2.0 on a Nokia X.
How To Install & other details:
Features of Lovi OS:
1.Android Core by CM
2.Comes with some pre-installed apps for perfect mobile productivity
3.Compact UIX inter-platform release
4.Lovi OS also comes with ‘Kingsoft WPS office for Android’ for perfect mobile office productivity.
Note: [Almost everything works good for Nokia X]
How to flash for Nokia X and XL:
1.Download the zip files/files for your device
2.Reboot your phone to recovery mod
3.Wipe data/factory reset
4.Flash the downloaded zip file
5.Flash the CM11 XL All Sensor Fix.zip(Only for Nokia XL)
For Nokia X2 you can use an easy tool to flash custom ROM. Here is a tool that makes rooting, recovering bricked Nokia X2 devices, Custom ROM flashing and even Google Play Store implementation quite easy.
ROM download links,
For Nokia X: https://drive.google.com/open?id=0Bz…HRMaTg4eG1paHM
For Nokia XL: https://drive.google.com/open?id=0Bz…29MZHNmMTBreEU
Camera Fix can be installed from here.
Sensor Fix can be installed from here