I am a serious Ham Radio operator and an avid Mac user and what I have found is there is a similarity in hardware.
Way back in 2010, I swapped out all Windows computers at work and installed Mac desktops and servers. It was the best thing I ever did. Why? Simply because they are easily upgradable, easy to operate but most importantly easy to update the firmware. Same is true with today commercially manufactured Ham Radio HF transceivers. Most HF manufacturers have moved toward Software Defined Radios (SDR's) for a multiple of reasons, one being ease of upgrade of firmware.
Therefore, it would not be far fetched to assume that the firmware in the stock Panasonic HU's in our 4R's is upgradable. What leads me to believe this is the Chinese aftermarket add on box that will allow screen mirroring of the iPhone, albeit with a tethered cord. If that is possible, then quite frankly, I believe it's possible to upgrade the firmware on the HU for either Apple Car Play or Android use.
Whether or not Toyota software engineers will work on the updates and pay the licensing fee is another question. What we all need is some young person with nothing to do to fiddle with a hack to make it possible. Remember there are 2 ports to make that happen, one where the SD card is for the NAV and the other is the USB port where you can upload pictures for the on/off screen.
OK guys, flames, comments?
UPDATE: Check out Toyota Service Bulletin T-SB-0279-17
My Runner was made in July of 2018 and is a 2018 model. Based on the model number listed on the bottom face of the radio, the radio is a 2019 model HU. The software number listed in settings is the same as the number in the TSB for 2019. Make some correlations and it "appears" that all units installed from 2016-2019 are similar except for firmware and software, which leads me to the conclusion that all units from 2016 through 2109 have the potential to be upgradeable. Whether or not Toyota will do that is a different story. I might suggest we start pushing the envelop guys and pressing some reps