HTC may not release a Android 4.4.2 ROM for HTC Buttery but XDA already has released this KitKat firmware
The ROM has variant of HTC Sense that comes on the One M8.
Requirements for flashing the ROM
* Unlocked Phone from HTCDEV or S-OFF
* Custom Recovery like TWRP or CWM and we prefer TWRP.
Features of the ROM
Latest HTC NEW ONE (M8) Sense 6 base ported to x920d
More languages enabled (FULL WWE)
Root, busybox and init.d support
Persistent ADB enabled
Ramdisk improvements
Battery life, performance and memory improvements
sysro / sysrw binaries
openvpn / sqlite support
disabled logging & removed bloatware
stripped debugging info for improved performance
optimized with latest sdk for improved performance
trimmed partitions for improved performance
zipaligned apps for improved performance
flar2’s Write Protection MOD to allow S-ON users fully writeable /system partition
advanced power menu
disabled Persistent Navigation Bar (m8 has it since it has no softbuttons)
5×6 Grid size option in Sense App Drawer
Sense Launcher Menu Support
Possibility to ODEX your ROM
Ability to map LongPress Home SoftButton for MENU in Settings – Display
optional show LTE icon instead of 4G
optional Disable Persistent NFC Icon
optional Lower Proximity Sensor Sensibility
optional Louder Speaker Mod
optional Stock Boot Animation
optional Exchange Email Hack (disable EAS Pin Requirement)
optional Disable HTC Color Enhancement
optional Show LTE instead of 4G
optional Disable Fast Dormancy
Smoothest ROM
Best Battery Management
Fast fixes / updates
myHUB with OTA support
InsertCoin Kontrol APP with unique features
Download from here and flash it using ODIN.