Teclast have just recently added Air 3G and Air II Android 5.0 dual boot firmwares for users to download via their forum. (Which is in Chinese) This is a beta trail of the firmware, so I can only imagine new Air II and Air 3G’s to start shipping from the factory in a few weeks with Android 5.0, wait for that announcement.
In the meantime if you are keen to flash your own Air 3G or Air II over to Android 5.0 and Windows 8.1 dual boot, visit the links below. Use Chrome to translate the page or your own translator. It would seem that a recent update for the Air 3G let’s users flash just the Android files and leaves your Windows installation untouched. That’s of course if you have the stock partitioning.
I’ll see if I can download the files and mirror them here on the server.
Android 5.0 / Windows 8.1 dual boot firmware and tutorial for Teclast Air II
Android 5.0 Lolipop update for Teclast Air 3G: Link
Flash at your own risk, If I can get this to work on my Air 3G I’ll post up a how to.