Android TV is not an open platform...
Google have specific Rules for interface design and app usage or you don't get on google play store...
The first rule SkyGo breaks is REMOTES must work the apps... it breaks a lot more as well...
SkyGO is only touch controll... The hole interface would need to be rebuilt....
luckly "TV from Sky" app WAS built to support Remotes and HDTV including licensing HD versions of content not all channels agreed and many were not licensed when it released... each platform has specific agreements so Even if and when android TV ever got agreed, it may not even be the same service level...
PS4 had missing channels at release...
Adverts funding + sky extra subs must equal a profit... and adverts are platform specific...
The Shields android tv box line official release was less than 6 months in the UK. The UK User base is not going to be big enough yet...
The PS3 had been out years and the PS4 had been out nearly a hole year so the user base had allready grown...
The PS4s super sell out release speed and direct rumored support from SCEI helped...
There is still a risk that Google would force a rebuild of "TV from sky" App for AndroidTV which will add extra developement costs again...
An example of a rebuild for these rules and the costs is Opera browser for Android TV on Sony devices it had to be rebuilt specific for android TV even after it was allready on the Google store and googleTV devices and Googles own web browser is not being recoded for android tv... Its their own browser but its not on Android tv....
Even the deal for SkyGo on kindle is still restricted to touch screen devices only, again the remotes don't work on the TV box with the app so no official way to controll the app... So no app on Kindle fire TV box...