For the moment buildroot is not ready. And like Batocera and other are based on buildroot, this can take some time.
My opinion, too much changes in Raspberry hardware from the last versions, so I dont want to talk bad about but for myself the PI4 will be the first Raspberry that I will not buy (and need) Much better to plan for the future with x86 boards. Next year will come aut the fanless J5040, cheap, 10W and with 3,2GHz, as example. No reason anymore to buy one of this trashboards coming out every few month. There are already some heat issues with PI3B+, and they now produce also a CM3+ with no higher speed as CM3. And PI4 will also not be a wonder box. Really money much better invested in a board 3x the price, and with trashy trashy trashy you finally spend more 🙂