Technically it's just 128 bits, it doesn't matter how you represent it. I've written this IPv4ES solution, which allows you to use 128 bit addresses using IPv4 format.
I see this just as repetition of the 32 bit vs 64 bit operating systems. Why would anyone want to use 64 bit operating system? Instructions are longer, it requires more cache, RAM, disk space and so on, making performance worse. Nobody actually wants 64 bit systems. Endless problems with drivers, programs, etc.