Palm OS will continue to exist for a short while in the Centro, but after that, it's done. Palm OS was never intended to work as smartphone software when it was created in the mid-90s. It was PDA software that kept having additional functionality packed onto it's modest frame, giving the core OS a lifespan of 13 years.
Dan Lyons said it best when commenting: "It was a bit like using a lawn-mower engine to build a go-kart, then adding a bigger chassis and turning the go-kart into a real car, then turning that into a plane, and then trying to make the plane fly to the moon." Here's a look at how the Palm OS evolved over it's lifespan. Rest in peace, Palm OS. We hardly knew ye.
Palm OS Timeline (1996-2009)