Ok, guys, this thing kept me awake till late, so I did some research, and here's the answer to all your questions...
When a USB device is connected it sends in a request to negotiate the power profile according to the needs of the device. The maximum supported by USB 3.0 is 4.5 watt (and not 10 watt).
The new USB spec simply moves the cap up to 100 watt as the maximum that a device can try to negotiate for (try is the keyword). Up until now no device could request for more than 4.5 watt from USB, such request would just fail.
This however imposes nothing extra on the USB, except not to send request-fail just because the device wants more than 4.5 watt. Instead, the request-fail will be guaranteed if a device wants more than 100 watt. But this doesn't mean that the new USB has to support more than 4.5 watt of energy. IT DOES NOT. The new USB must prove provide the output: 4.5 <= Output <= 100 watt.
To give it a good life example. Up till now when you are buying a device that provides USB 3.0 ports you didn't care about the maximum output on those ports, because they were supposed to provide 4.5 watt each, even if in practice that didn't always work, depending on the manufacturer and the controller. But now you will also be paying attention to the maximum output figure you can get from those USB ports, either separate or combined, so you can run it up against the devices you plan on marrying it with.
This does complicate things for the end user, as now one has to pay attention to the extra specification parameter, as each device with new USB ports will have its own cap somewhere between 4.5 and 100 watt, according to its spec.
I hope this clears things out.