Isn't situation same as with Bluetooth with HCI mode where complete stack must be implemented in PIC?
For Bluetooth this is quite a lot of code and WiFi is much more complicated. I suppose that PC WiFi modules only have PHY and everything else is in PC driver. When wireless module has SPI than it means (mostly) that most of stack is placed into intenal MCU. For example Bluetooth modules have some ARM ticking on 200MHz doing job. With quite a lot of memory.
For Bluetooth this is quite a lot of code and WiFi is much more complicated. I suppose that PC WiFi modules only have PHY and everything else is in PC driver. When wireless module has SPI than it means (mostly) that most of stack is placed into intenal MCU. For example Bluetooth modules have some ARM ticking on 200MHz doing job. With quite a lot of memory.