Definitely not all live and functioning. In fact I suspect less than 10m are actively used. It is a company that has been around for years and it has run into sales issues that last few years with competition and their products have tech product lifespans of around 3 years I suspect.
Personally, I have a Roomba I bought in Jan 2019 that's still doing just fine (So 7 years now).
Most of the parts are pretty easily replaced (genuinely pleasant surprise, as an aside) and the company stocked most replacement parts for a long time - I just checked again and I can still get parts for my model (I-series) incl batteries, wheels, brushes, filters, etc. Which is less than it used to be, but still enough to keep mine rolling around for another 3ish years without any likely problems.
And that's outside of the whole "unofficial" replacement parts ecosystem that popped up online.
3 years doesn't track with my experience on this one. I'd bet it's 5 to 10.
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For context, Amazon tried to buy them for exactly the same purpose ~2 years back (home/house data) and failed to get EU regulatory approval, so scrapped the deal.
I'm not thrilled to have ownership transferred to another company (I was also very unhappy to hear the Amazon rumors back then) and I think this is a pretty clear risk.
Even if a user is no longer using the device, Roomba still likely has plenty of data about their home floating around.