We've shipped more than 3,000 developer devices so far. (androidcentral.com)
The ASUS - made Nexus Player first debuted in November of 2014, and it's remained the only developer device for Android TV, remaining on the bleeding edge of the OS despite it's aging specifications. (9to5google.com)
Even Google's Nexus line of devices, intended as developer devices, have locked bootloaders. (howtogeek.com)