The implications for literally the entire manufacturing sector along with any importer of goods are so significant that you can guarantee a loss in the disputes tribunal would result in an immediate appeal.
The consequences of a loss in a case like this would be massive. Imagine how much you'd need to pay for a phone if manufacturers had to keep giving you a free one every 2 years when the current model was no longer supported. What happens when YouTube no longer works on your 5 year old TV because Google change their API? Will every TV manufacturer need to give away a free TV every 5 years?
Considering the value of the case and that the disputes tribunal does not involve lawyers I suspect appeal would not be a big issue.
I don't agree. To take your example, they wouldn't be giving you a "free one" every 2 years, they would be supporting the original one for 3 years (which they should do already!).
And yes, if Youtube stopped working on their TV that was advertised to have Youtube then it should be replaced within a reasonable lifetime. If however it was not advertised with youtube and this was just a app downloaded after the fact then no, it should not be refunded/replaced. This will just force them to ensure updates and make arrangements to do so rather than focus just on the immediate sale.
It's quite simple, if it can't do it for a reasonable lifetime, don't sell it.