No, the Pro-164 is not technically capable of working with P25 Phase II communications and a simple firmware update would never provide that capability either. The hardware necessary for doing that type of decoding is simply not present in that scanner. It's not capable of P25 Phase I decoding either, for that matter, it's a traditional analog only scanner.
Having said that, it is possible to create what's known as a discriminator tap which taps into the baseband pure raw signal the receiver is pulling in (before it gets processed by any audio circuitry and filtering) - you could then feed that discriminator tap signal into a computer's sound card and use software on the computer to decode P25 Phase I traffic using DSD+ on Windows, and if you really need P25 Phase II decoding capability that's possible using OP25 on Linux (it's not a Windows application and most likely never will be, sadly).
It's a more complicated process, definitely, and requires a bit more effort to do all that for P25 Phase I/II monitoring but it is possible to get it done but the Pro-164 by itself can't do it and never will.
Another solution for decoding P25 Phase I/II comms these days is using one of the "cheap USB TV tuner" sticks, typically $10-25 each (more expensive = better performance and sensitivity) along with DSD+ (again, on Windows) or OP25 on Linux to get the same task done. Yes, it's even more complex than using a discriminator tap would be but it's also vastly more capable as well in the long run. And yes it does require a computer to be the basis for all of the functionality but considering you're posting here on RR there's a really good chance of you already having one.
Just some possible options.
