Yes, there a practically no limits.
You need devices that are a perfect match for the current content from providers AND offer something that offers and opportunity to deliver content to people without the need of a multitude of devices that only confuse them, are expensive to support (different manufacturers, firmware improvements) and and are hard to use for the average consumer.
The TV itself is just hardware, the box is where the magic happens. Apple sold TVs can include the same hardware specs as an Apple TV, but I would consider this a second step, because they need to have a device that creates the opportunity first, after that, you can sell a TV that MAKES USE OF IT, without having to deal with dozens of TV manufacturers and confusing, needless specs alone.