For some reason the patent clock rarely starts the moment a technology is known. MPEG-1 was published in 1991, but patents on, for example, MPEG Audio Layer III didn't expire until 2012 in Europe, and 2017(!) in the United States, 21 and 26 years after the standard was released. While there's been some patent reform since then, it's still the case that a standard can be published in the middle of patent applications, and the 20 years doesn't start until the application is approved, which can be years after publication.
So don't count on any of this being OK in 2034.
It's a shame the expired codecs didn't have mechanisms for, say, HDR, as I suspect with bandwidth availability becoming so cheap, and CPU power better than ever before, it'd be nice to be able to switch back to a simpler, albeit less efficient, codec with no legitimate patents still applying like MPEG-2. Unfortunately even trying to graft HDR onto it would be a problem - the ITU did apparently add something in 2014, but that means you won't be able to trust it until the late 2030s...