I can only imagine they'll be a big rush to create decent procedural objects for this engine now.
Yeah, i actually work on terrain generation since quite some time now.
HQ hightmaps as seen in the Gaea tool is quite easy to do. But as we zoom in more closely, the surface of rocks is formed mainly from fracture, which is much harder to simulate than erosion.
The modular composition workflow as proposed by UE5 adds another obstacle: Real world terrain is formed from global relations - you can not easily resemble the resulting flows and large scale shapes from repetive small scale modules.
The alternative is to simulate at global scale, not using modules. But then detail becomes difficult because storage limits.
Generating Quixel quality assets procedurally surely is hard. ML does quite good here (seen many papers), though it needs samples (expensive) so it limits creativity if we want to create non earth like worlds.
So, i'm into the simulation approach, because it needs no input and can generate from zero. (Knowing nothing about ML i have no choice anyway)
So far my experience is this is very promising, mainly because computers became so powerful. Traditional works (also NMS) were restricted to things like perlin or voronoi noise, but simulation can generate those same building blocks at much higher quality, and having that realistic flow which was missing before. It feels there are no limits on one side, but on the other side i'm constantly lacking ideas on what to do exactly to get expected results.
But mainly i feel like we are at a paradigm shift where procedural generation is ready to finally take off, solving the obstacle of boring and uniform results we've seen in the past. We don't have an option anyways - scanning and compositing is still too limited and too much effort on the long run i think.
For UE5, automatic placement of quixel assets over a hightmap really seems necessary, but even if detail is 'unlimited', results won't be convincing in many cases.
