The upshot of this is that we are likely to see multiple device architectures suited to the user's need. The blogger worries about Sony, but he doesn't need to: Their readers with the B/W e-ink screens are perfectly suited for paperback reading. In the meantime, OLED or color e-ink will be applied to new readers, probably larger in size, that will be better suited for magazines, textbooks, comics, etc. Sony can always sell both readers, targeting each to a particular consumer. There's plenty of room for devices of both types out there.
OLED may be good, but I suspect color e-ink will prove better for readers... and there are other technologies out there that may still emerge as superior to, or at least competitive with, color e-ink (for example, Qualcom's
Mirasol displays).
And although the "fresher" generations may prefer converged devices, there's no reason to assume their device of choice will be small. A larger device, possibly with a built-in phone and included hands-free earpiece, is as likely as a cellphone- or PDA-sized device to be successful.