XDA forum member pabx has ported Android 4.2 Jelly Bean to HTC One X. This is not official ROM by Samsung and few features may not be working as it is the preview build.
As per the source page-
GSM Data (still needs some more testing)
Video Playback (including HD)
Audio recording (= no VOIP, crashes the audio subsystem)
Fails to boot on phones running HBOOT 1.31 (if you have hboot 1.31 and would like to have this fixed: please join our IRC channel)
Installation of paid applications
..and probably some other things.
Let us go through the guide to install Android 4.2 Jelly Bean ROM on HTC One X.
The guide and ROM mentioned below is only for HTC One X and cannot be tried on any other device.
We cannot be held liable of any damage done to your device while following the below mentioned procedure.
Install Android 4.2 Jelly Bean ROM on HTC One X
Take a complete backup of data,apps and settings as the procedure may wipe your data.
Make sure that the battery of device has a minimum charge of 60%.
Enable “USB debugging” on your device by going to Settings >> Developer options >> Enable USB debugging.
ClockWorkMod (CWM) recovery should be installed. Go through the guide here to install.
Unlock bootloader on HTC One X.
Download HTC Sync on your computer to install drivers.
Download Android 4.2 ROM from here and Flash_Boot.zip file.
Copy both the zip files to SD-Card on your device without extracting.
Extract “Flash_Boot.zip” file to a folder and extract “boot.img” file from Android 4.2 ROM file and copy it to the folder where you extracted “Flash_Boot.zip” file.
Switch off device and enter bootloader mode by holding Volume Down button and Power buttons. Select the option Fastboot using volume buttons and power button to select to enter fastboot mode.
Connect device to computer. Open Flash Boot folder and run “flash-boot-windows.bat” file by double- clicking which will flash the required boot.img.
Once the boot.img gets flashed, select bootloader and then select recovery to boot into ClockworkMod recovery.
Select “wipe data/factory reset” and wait till the data gets wiped.
Select “install zip from sdcard” and then “choose zip from sdcard” to install the ROM. Wait till installation gets complete.
Select “go back” and then select “reboot system now”.
Android 4.2 Jelly Bean is installed on HTC One X.