Obviously you haven't tried watching on your Nexus 7 lately. (If you let it update, it doesn't work. No support for Android 4.3.)
I would like to see HBO Go. However, unless there is some standard app that can be used on the Tivo, it isn't likely to happen. There are very few devices that can do HBO Go and they are all extremely popular compared to Tivo. I am sure, just like the Amazon Prime app, Tivo just doesn't have the user base for them to justify coding for them.