You can now download Nexbox Z68 firmware for manually updating your android TV. This android TV is capable of playing 4k video at 60 FPS thanks to HDMI 2.0 support. Nexbox Z68 currently retails for about 50 dollars on most chinese online retail sites.
You can download Nexbox Z68 firmware from link given below. Then follow the steps given in CR18 android TV post to flash it.
Nexbox Z68 specs include Android 5.1, Rockchip R3368 Octa Core up to 1.6GHz (Cortex-A53 64bit), High performance GPU,support OpenGL ES3.1, OpenCL 1.2 and DirectX 9.3, DDR3 2G RAM, Onboard eMMC Flash 16GB, 2.4G /5G WiFi, 10/100/1000M LAN and 4Kx2K + FHD 1080P@60fps video output. Supported video formats include MPEG-1, MPEG-2, MPEG-4,H.263, H.264, AVS, VC-1, RV, VP6/VP8, Sorenson Spark and MVC 3840*2160 60FPS.
Port selection includes 1x HDMI, HDMI2.0 Full HD 3840x2160P, 2x USB 2.0, 1x SPDIF, 1x Micro SD card (TF card) reader, 1x RJ45 LAN Port and 1x 5V 3A DC. Box contents include tv box, IR remote control, HDMI cable and power adapter.