Last of a dying breed
I suspect that e-ink is on its last legs. Tech like Mirasol is likely to make e-ink look antiquated and it can't be long either before something appears to use it. Failing that I suspect most people would prefer OLED / LCD over e-ink even if the latter is more readable outdoors and uses less power.
On the subject of this device, I have a previous gen PRS-350 and it's amazing how much difference touch makes to e-readers. Most ereaders are festooned with buttons to speed up the sluggish UI, but IR touch works remarkably well and accurately. I don't know if wifi would do much except for people who want stuff delivered to their device automatically but it might allow Sony to make enough coin to subsidize the device to Amazon levels.