PalmSource's numbers come from US market watcher NPD, which tracks retail sales. During March, 47 per cent of the smart phones sold in the US through retail were based on the Palm OS, 20 per cent were based on the Symbian OS and the Series 60 UI (ie. Nokia and Sony Ericsson) and another 20 per cent used either of Microsoft's two smart phone-oriented Windows Mobile variants. PalmOne pledges to boost Treo shipments | The Register
I've predicted the demise of Palm-based smartphones multiple times now, but that is likely because I keep thinking about European uses.