Will web developers be needed for the internet of things?

Yes.
The internet of things will be dominated by embedded systems. Assembly, C, familiarity with linux, and basic web skills. RF fundamentals will be handy too. A degree in computer engineering will likely be the best entry point. The internet of things will require a programmer to be very familiar with the hardware.

Yes, because even the IOT will need management interfaces.

Specific skills: hard to predict, because the IOT is such a new and immature concept.

Would someone care to drop me a clue about what differentiates the IOT from, you know, the plain old internet, period?

When did the IOT become a thing and why? Just curious.

The IOT is where everyday devices such as your thermostat, garage door opener, refrigerator etc are internet connected.

Thanks for clearing that up.