Ok, let's step back and have a look at the big picture here. My son's 4s has the WiFi greyed out issue and thus began my search for information. I know someone else who also began experiencing this problem last week.
After reading many of the symptoms/remedies of the problem here and elsewhere, it is obvious that this is a hardware issue. There are many early reports of this problem and they were determined to be a hardware related issue long before the release of iOS 6.0. There also appears to be a correlation with the hardware issue and the release of iOS 6. The symptoms of this defect are consistent with a poorly soldered/connected WiFi component. Heating/Cooling reestablishes the physical connection for a short time. This physical connection could be reestablished just by shaking the phone. Toggling settings on/off when the physical connection is reestablished corrects the problem as the software recognizes the "new component". It has also been suggested by others that the iOS 6 release may have exposed, exacerbated or caused this problem. Due to reports of owners repairing their phones by heating them to high temperatures, it is likely they are melting the solder and fixing the physical connection. The melting point of common lead free solder is about 180C/360F. It should be possible to achieve this temp with a blow dryer. There also have been reports of short battery life with iOS 5. Short battery life = high power usage. I know that turning off WiFi will significantly reduce battery usage.
How did the connection break? Poor solder, poor design/engineering, electrical/thermal fatigue, physical damage or a combination of factors.
It is possible the solder joint had somehow become weak and a high demand was placed on this connection causing it to fail. This high demand could come from a SOFTWARE DEFECT. Depending on environmental factors of each device the life spans would be expected to vary. The time of failure after loading new iOS could vary and may not be immediate.
It would be interesting to see the time line of device failures. Are the oldest the most afflicted? Will a new 4S that has never run iOS5 fail?
Many users never use WiFi because they have unlimited plans. How many people have gone over their data plans due to this failure?
Certainly engineers tested the new OS. Did they test it on older phones?
The facts:
- The 4s is the phone with the WiFi/BT problems.
- The 4s was released 10/12/11.
- 4 million 4s sold in 1st 3 days and many million more since.
- 4 IPhone 5 released 9/21/12.
- iOS 6.0 released 9/19/12.
Many 4s's will be out of warranty soon after the release of iOS6. The replaced devices had only a 90 day warranty.