Apple have always described the Apple TV set-top box as "a hobby" and it doesn't look like that's changing any time soon. According to Apple COO Tim Cook, the company is aware that the next logical step for Apple TV is to integrate the functionality into a standalone HDTV; however, that's not a step they're interested in taking.
"Today, the go-to-market model for Apple TV is very difficult. Because it would seem that that go-to-market model would lead to the TV. And we have no interest in being in the TV market" Tim Cook, COO, Apple
Nonetheless, the company also isn't keen on putting Apple TV out to pasture, since people at Apple - Cook included - reckon it has potential. "We're continuing to invest in it because our gut tells us there's something there" the exec explained, "there's people - and I'm one of those - that they're avid Apple TV users, and so, because their gut says something there, we're continuing to invest in this."
A recently posted job advert from Apple suggested that the company is looking to expand its product base for devices running iPhone OS, and the Apple TV was one of the speculated recipients. That would certainly open it up to greater flexibility in terms of App Store access, but the UI would likely need to be significantly reworked in order to suit the usage model.