It seems completely incompetent, but makes sense if you believe they're going to be acquired this year.
Ben Einstein said last in July 18 (https://blog.bolt.io/sonos-one/) Sonos are "a traditional speaker manufacturer incrementally adding technology in an attempt to keep up with a fast-moving race". Sonos probably still have the best multi-room speaker solution, but 1) their lead on that is slipping, and 2) I don't think new buyers care about multiroom as much as they do streaming services & features - i.e. the bits Sonos must be being squeezed on.
Their proposed solution for customers with old devices is a software-managed network split between old & new - that will kills multiroom playback for holdouts! That's the worst of both worlds - Sonos paying programmers to prop up old devices, while owners still prepare to see a fundamental degradation in their system.
Then the tie-in with IKEA seems like an enormous dilution of their brand. Now you can buy Sonos components from IKEA, and the IKEA home app can also control all of your Sonos speakers (not just the IKEA ones).
So that's that I think they have a deal in the works (IKEA?) - and they're massaging a few quarters to show briefly increased profitability while the long-term vision can go to hell.
In that light, cutting off old products in the face of so many angry customers makes sense. They remove a legacy support liability instantly, allowing them to be bullish about future R&D costs. And the angry customers are the ones bought into Sonos' 15yo product vision - they just may not represent much future revenue.