Epic only ever implements gpu-agnostic solutions into the main branch and I don’t see that changing anytime soon (I can agree to it, it’s not good to alienate users because of their specific hardware)
so if RTX only works on nvidia cards I guess it will stay exclusively in the Nvidia UE4 branch (gameworks etc).
or -maybe- RTX works on non-nvidia cards but just really slowly (like software rendering), which would kinda be ok to get integrated into the main UE4