Apple could also differentiate from Free TV "Channel" apps and Paid ones in the Appstore. Free channels apps would monetize through commercials. The paid ones would be subscription like HBO, etc. The TV channels could monetize even better because there's a direct relationship with the customer/viewer and they can target ads more specifically (location, demographic, age, gender, interests, etc).
In the end, Apple's new TV will be just a screen giving the user access to "channels" which will be apps.
Also, the apps might have two interfaces: one for iPad/iPhone (or separate) and also one for the iTV. The iTV interface will be really simple and will list out all your TV apps and what's playing or what's popular recently.