Yes, we're needs to wait until someone who has radio with new bootloader will test it and there is no guarantee that it will works and will not brick the radio. But it's better to test it on one device and share results to other, so other peoples will know if it works or not and can avoid unnecessary risk of bricking the radio. If it will be tested by many peoples and it will brick the radio, it leads to a lot of bricked radio and it will be a stupid way...
I estimate the risk is not high, and if I had a radio with a new bootloader, I would test it without hesitation. The price of the radio is 15-20 USD and you don't lose it, you can use its component as replacement part for other radio (battery, charger, enclosure, antenna, PCB with all working elements include display, etc). And you can fix its firmware later, when new bootloader will be supported in a new flasher tools. So, I don't see there a big lose.
I expect that if it don't supports old flash write packet, it just will fail on first write packet and it don't brick the radio.
But there is some risk that it can brick the radio, and there is needs to be ready for that, this is why I don't share the test tool with new protocol support and will share it to the one people who understand it and is ready for that. If there is no such people, we're needs to wait when some other people will get the radio with new bootloader and will do research how it's new bootloader works. There is no other way...
By the way. Did you tried to read EEPROM from the radio with new firmware 5.00.05?
If it don't works, can you share k5tool log file for -rdee command?
Note: EEPROM read should be executed when radio is working in normal mode, not bootloader