You'll have to wait until S2 arrives to find out.  Sonos hasn't even confirmed that high res audio is coming.

So far, the only official information from Sonos about S1 and S2 are in the two FAQs they’ve posted, here and here.

My understanding is that any unit that is considered Gen2, will get this update.  How to know if you have Gen1 or Gen2?  This article spells is out- really easy to do:

https://en.community.sonos.com/components-228996/how-to-know-if-my-connect-is-gen1-or-gen2-6837988

Your article is specifically about the Connect, while OP is talking about his Playbar...different products.  As well, I don’t think the question is about whether the Playbar is S1 (legacy) or S2 (modern) as it definitely is S2, but whether it will be able to play hi res audio through future updates.  That question doesn’t have a definitive answer yet.

I think, as quoted here, “we’d be amazed if the upgrade will not support high-res”…

https://www.whathifi.com/us/news/new-sonos-s2-platform-paves-the-way-for-hi-res-audio

Correct.  Not a definitive answer. 

Here is another speculating article- rumors of new beam/sub and Play 5 coming out this summer as well…. which brings up all kinds of questions- will the current Gen2 Play 5 with the S2 upgrade patch applied, be “equal” to this new Play 5 that will come out? (same question for the Beam and Sub I guess)….

https://www.whathifi.com/us/news/sonos-rumoured-to-launch-dolby-atmos-soundbar-very-soon