The question on my mind is will the SoundTouch app continue to be supported on new mobile OS versions ?

Is it the same app that caters for other speakers too ? If it is, and Bose continue to include their old speakers on the functionality of the app, then I can hardly see how this is a true EoL. They’re really continuing to support the speakers in their app, at least.

They're discontinuing support for SoundTouch Speakers. The SoundTouch App controls SoundTouch Speakers. Put two and two together...

From their announcement:

  What will no longer work:
    • Presets (preset buttons on the product and in the app)
    • Browsing or playing music services directly from the SoundTouch app
  
  Important note: Your system will no longer receive security and software updates.
  Please make sure to always use your system on a secure, private network.

Considering that new speakers don't use SoundTouch, I wonder too. I hope that they keep the app running for a while. This kit is expensive and it can't have a short life time!