Can customers use the same wireless power coil and add firmware to the IDT receiver for near-field communication (NFC)? 

At this time, it is not possible to use same coil and customer firmware to do NFC. The antenna design of NFC, frequency, and communication protocol is significantly different from the WPC Qi and PMA standards.  In the future, it may be possible to use a combined coil, or a coil module that contains both coils together.