From Farhan's post of    https://groups.io/g/BITX20/message/73708
>  The V6 is just an easier to assemble v5. No difference at all but for the touch display.
>  You can buy the tft off ali express for about 5 dollars and upgrade the firmware.

So the answer is yes, you can update a v5 to have a v6 style display.
No need to swap out the entire Raduino, just the display itself.
Then burn the v6 firmware into the Nano.

I believe the Raduino board has not changed since first introduced for the Bitx40,
except that now a socket is used on the Nano to make it easier to replace.

The old 2x16 display just plugs in, hopefully the new display can plug into
that same old connector with no soldering necessary.

In the past, it has been possible to buy a Raduino separately from hfsignals for about $30.
I don't see that as an option on hfsignals.com now, the only items to buy are the complete v6 uBitx and the Antuino.
But if the display is easy to swap out, and the Nano is socketed and thus easy to replace if it fails,
that covers most of why you would want a new Raduino. 
About the only other stuff on the Raduino is connectors, LM7805 regulator, and the si5351.
If you really do need a new Raduino there have been third parties posting to the forum
offering their own version for sale, some of them with significant enhancements.

Jerry, KE7ER