To all the people talking about ownership. I find it hard to believe the aux in will cease to work. So worst case is they turn into regular speakers.
What it sounds like is you won't be able to update your firmware. So more likely than not, everything would keep working but random Internet related services (like Spotify Integration) may break over time because, for instance, if Spotify changes their API you won't get the software update to fix it.
And that is why I think it is OK. Software updates over the Internet are always subject to licensing. That is not new and not unique to Sonos.