What are you expecting the updates to give you, functionally? They wouldn't be adding more hdr, dolby, and 4k functionality that it might be missing. Your best case scenario is that any updates don't further slow down the TV. If you're going to be a power user with all of Android's functions, I would just add a Shield.

I buy televisions for the display, and nothing else. I might as well throw away the remote when I buy one.

I use a Shield for Android. Constant updates, everything works perfectly.

A 4 year old tv probably won't get updates, it's probably outdated already. And it might not support the latest standards (as 4K, hdr etc.)

I'd rather get a new cheap tv, than an old top model at a decent price.

Mine is 4 years old and just got an update. Sony Bravia xbr65x930d, 2015 model.

IF everything works as it should, why do you need updates? You wouldn't expect them on a 4 year old Android phone either. I don't even use latest updates on my Shield because I'm happy just the way it is.

I wouldn't expect many updates. See how it runs you might want to end up getting a Mi Box S or Shield TV.