Electronic – Is it possible to have a device with metal case and wireless charging

It is still fairly expensive to add to devices.

You have development time and cost since cell phone companies have never added this feature before. I would have to imagine the cost to do this is fairly significant. Cell phone companies will have to do a fair amount of testing to insure that the charging doesn't have any adverse effects on the phone. You can argue that there are already people using these types of chargers on phones, but you have to keep in mind that these systems are still outside of the phone for the most part. When you bring it in to the phone itself there are potentially areas of issue, like inductively coupling to data lines that are already pushing the limits of speed, any extra unwanted noise can be very bad.

You have the cost of the IC and board space. The IC is about $3.50 each. And even though the ICs biggest claim is how small it is, you seem to be forgetting that this IC is new so no one has had a chance to use it yet. But even with how small it is, board space is limited. Figuring out how to fit it all in is extra engineering time and the extra component is slightly additional fabrication cost, maybe only less then a cent more, but these companies are already counting every penny. As @stevenvh mentioned, if you have wireless charging you can remove the external power connector which will save lots of space. However, people still want a USB port. It will be a little while before people are "ok" with the idea of just using bluetooth to transfer data between the phone and computer. In fact there are still phones out there now that have their bluetooth so locked down that you just have to use a USB cable in some situations.

Public view still is not great. There is a large amount of people who are very much against the idea of wireless power. Reasons behind it range from it being less efficient to it causing cancer. You can try to debate these points all you want, but it isn't going to change the minds of people in the general population.

So overall, extra cost that just results in not much gain (at least as of now).

For maximum sensitivity, an antenna would be sized to the wavelength of the incoming signal. The sizes of most wires (traces) in a phone's circuit board are too small by maybe 2-3 orders of magnitude to be a good antenna for the wireless power signal. The size of wires inside the chips would be orders of magnitude smaller than that. The wireless power receiver wire loop is sized to resonate with the transmitter, and has circuitry to actively guide resonance. The frequencies involved in wireless power are very low compared to most of what's going on in a phone - kHz compared to GHz.

Any digital processing would be immune to noise so long as it remains well below the threshold of creating bit errors. The more sensitive parts of the phone to wireless power would be the analog areas, such as RF receiver and audio. Audio would be especially susceptible as the signal frequencies are closer together, both in the kHz range, although possibly still one or two orders of magnitude apart (4kHz for voice vs 100?kHz for power).

Most people don't use their phone while it's on the charger, so whatever problems are caused wouldn't usually be noticed, so long as no permanent damage is caused. Worst case scenario might be some missed calls, or bad-sounding audio if charged while connected to the stereo.