It's about more than security updates. And this may seem off topic, but bear with me for a moment.
Smart devices, including but not limited to Smart TVs. The manufacturers need to be legally and financially liable for damages caused by their devices getting hacked and used as a botnet.
When I buy a toaster, I have a reasonable expectation that it won't burn my house down.
When I buy a Smart TV, I have a reasonable expectation that it won't get hacked, become part of a botnet and cause massive damage to someone else, far away that I don't even know.
It is not impossible to build a very secure IoT device. Anyone who has ever gone through PCI compliance to build a web site or anything else that accepts credit card data knows this. It's not impossible. It's just a very high bar to jump over. Demonstrating a similar level of security should be enough to be able to get insurance in case your IoT devices do get hacked and cause harm.
The costs of this would be passed on to consumers. This would make Smart TVs more secure. But I'm also happy to pay more for a toaster that doesn't burn my house down, instead of a super cheap one that is dangerous.
This would either kill smart TVs as an economical consumer item, or it would make them very secure. If it kills them, then the data / privacy issue is solved -- to move this back on topic.