In reference to Qi inductive charging, I work with this stuff. As of now the Qi specification defines two power profiles, Baseline (5W) and Extended (15W).
The 15W is relatively new and the ICs needed to implement it are hitting the market now. Thus, we should start to see soon the actual charging pads, built around those components.
However, to take advantage of the higher power capability, you need also a receiver IC that can handle it. So it is a combination of having a 15W charging pad and a phone/tablet/other gadget with a built in 15W-capable Qi receiver.
As for the heating issue, a good 5W Qi system has an end to end efficiency around 75%. It means that to have 5W on the receiver side (1A of charging current at 5V), you need to have around 6.7W at the input of the charging pad. The difference, 6.7-5= 1.7W is lost as heat and most of the losses are in the magnetic coupling of the coils, not in the electronics.
I haven't tested yet a 15W system, but assuming similar efficiency, the power loss would be around 5W (20W input are needed to get 15W output). I can see how just the copper in the coil and the coil mechanical assembly may not properly dissipate that kind of power in a small closed enclosure. Hence, the forced cooling via fan.
