I don't get the price/poor argument. It's not like the devices won't get better (meaning cheaper), many stand alone GPS devices are actually usable as multipurpose gadgets, it won't be a long time until dumb phones are just smartphones with features disabled (because it would be cheaper), and tablets are likely to get in the same price spectrum as e-book readers. With all this in mind I fail to see how the existence of poor people will stop the more expensive devices from disappearing?
Sauce for the goose: standalone GPS devices will ALSO get cheaper, enough that you could buy one from Radio Shack for $15 and stick it on a used car you only paid $1200 for. Same again for tablets and readers: by the time you can buy a tablet for $200, the price of an e-reader will have similarly reduced to where you can buy a relatively good one for $50 and still have some basic tablet-like features. And the smartphone thing is just plain wrong: most smartphones are actually fairly expensive to manufacture in the first place and selling them with their features disabled isn't marketable; nobody's going to pat $150 for a prepaid phone that doesn't actually do anything, not while a legitimately STANDARD phone is available down the street for $39.95.
It really boils down to this: there will ALWAYS be a market for low-end products, and there will always be a distinction between the two. The form of the low-end market may change over time, but the low end and high end products rarely overlap. Where there are consumers who are thrifty or cash-strapped, there will exist a market for a "lesser" product that trades functionality for affordability and you will not be able to satisfy that market just by re branding yesterday's high-end products.
This is the reason why the iPod shuffle still exists, why the X-BOX 360 and the PS3 are both sold in various versions with various hard drive sizes and features. It is why after all these years you can STILL buy a TV that isn't HD ready, and why HD-DVD and/or Blu-Ray isn't going to replace DVD any time soon. Not everyone who shops for a steak is going home with a fillet mignion.