The Youtube app on Samsung SmartTvs is pretty good. I'm not sure who does it, but it has quite deep integration with the Youtube Android app and site, so it could be done by Google.
For example, you can pair your TV with your phone or computer, and then use the device to navigate Youtube but the TV to display videos.
It's YouTube's html5 leanback experience. So it's Google, but they license the interface to a lot of vendors. Google can in theory push updates out this way too.
This is also what Netflix increasingly does (Hulu Plus and Pandora too).
If a smart TV or set top box has a good version of WebKit embedding in it and uses html5 rather than embedded versions of code, they can stay up to date much better. Samsung's newest TVs are designed this way, but there might be a provision check for the Samsung website as was the case in this thread, which is just bs.
The problem was the first two generations of "smart TV"software were highly proprietary embedded systems with custom apps from a service. It took 7 years, but most have moved to html5.
You do still run into hybrid solutions. Even the Roku3 and TiVo Roamio have html5 for some apps and custom old-ass shit for others.
For the fire TV, Amazon uses html5 for its own apps but android apps for other services (except YouTube, who doesn't offer its app outside of google play, so it's the html5 version Roku and some of the TVs use). In that case, I wish for companies with great html5 solutions for those with them (pandora, Netflix, Hulu Plus)
For example, you can pair your TV with your phone or computer, and then use the device to navigate Youtube but the TV to display videos.