Legacy compatibility is such a thing. With old stuff, all you need is an old device and the software, and you're set. I have an old laptop for that purpose: Win95 (runs DOS natively) and parallel port and disk drive. Any old device software is archived on the internet and freely available. You can always find cheap replacement for the hardware.The LS60 does not need the app to work. It will need it to make changes like sub crossover or EQ settings. But, it has a remote control and you can always connect other devices to it. So, in 10 years if Airplay, Tidal/Spotify connect, or the built in apps no longer exist you can still connect an eternal device to it and control the source selection and volume with the remote. It does not turn into a big paper weight. This is also true of many smart TVs. A number of them after a few years their built in apps are no long supported. I was at a customers yesterday and said Hulu on their TV app no longer worked. Solution, add a streaming box, Roku, Apple TV, Firestick, etc. They had already done that and I have seen that happen many times with TVs.
It is certainly possible the built in apps will no longer work someday. Maybe there will be a new technology so Airplay and the various Connect service no longer work. But, you will always be able to connect an external device and the speaker will still work. Hopefully, even an old version of the app will let you make changes for EQ, etc.
That may no longer be possible with Android and iOS or even newer Windows/MacOS based stuff. It's all getting more and more nerfed and closed and downright jailed. Try getting an APK for your needed app, "sideloading" is going to be made impossible, on iOS you can forget it for years now, etc.
You'd need to be a hacker to make it all work indefinitely, and even then it's often impossible because you just can't get the software. I'm not going to buy anything that relies on an app, for that reason alone.