Obviously, Houdini to Unreal makes perfect sense is the most logical way.

But what about the other way around too? Being able to go from an unreal layout or sky clouds setup to Houdini for a second pass quality increase makes so much change today in the Film virtual pipeline, im surprised no one asked before or there is no way out today. Unreal is great for a first block out, it has better artistic and interactives toold than Houdini or other DCC (the sky and clouds system is a great example. Being about to shoot with a picture close or same as the final output in a virtual production shoot is precious too but it's likely not good enough for client approval and true photorealism

The sly/clouds systems in Unreal 4.26 is really great and there is nothing like close to this in other DCC. What will be possible to export from Unreal (poly mesh with volumetric texture baked per frame with velocity field will be ideal) to keep working in Houdini on the Unreal base and refine the result?
Hope Nanovdb will be supported in Unreal as for now selling volume on 2d cards stacked together is a little limited… That's will a huge step forward make films and realtime tech come even closer