When the pi3+ came out it was said that a total rewrite of the core was required (I may not have the terminology correct). Are we looking at the same type of rewrite required or will this be something akin to recompiling the code to recognize the new hardware?
^^ This is entirely new hardware. Different CPU, Different Ram, etc. And since the Recalbox crew took like a year to make it compatible with the Pi3b+, I don't expect Recalbox to work with the Pi4 for a long, LONG, LOOOOONG time.
But when 2020 or 2021 rolls around and Recalbox does finally become compatible? I'm sure it'll be amazing!
Also this claim of the Pi4 being compatible with existing Pi products? Horsecrap! None of the existing Pi3 cases will fit, none of the existing Pi3 software will work, etc.