Autoblog's comment on their most recent podcast was that Scion was a marketing experiment that has just about run it's course...
That's actually pretty accurate. The xB and the xD, the bread-and-butter of their sales, are basically reskinned Toyotas (Matrix XRS and Yaris five-door, to be specific). The only meaningful difference besides aesthetics is the Corolla engine in the xD instead of a Yaris engine, but otherwise it's a five-door Yaris. Adding new bodywork and a new name to an existing model...isn't this what GM has been extensively criticized for doing?