Yes, I think that sounds sensible to me — mainline U-Boot won’t boot Edge on its own without the ddr4 support, so Jagan’s epic 99-patch lpddr4 series is effectively a dependency.
Nice to see that the existing ddr4 work is completely sufficient to get Edge booting though; there don’t seem to be any other ‘gotchas’ lurking in the shadows!
Given the working device trees in -next and therefore Linux 5.3, it looks like the next releases (Linux 5.3 and U-Boot 2019.10) will fully support Edge in mainline without further patches.
(I think the one remaining issue to debug is the problem with the bcm4359 wifi chipset on the brcmfmac driver. It’s on my list to play with soon, as it’d be nice to get that bug fixed too in time for 5.3.)