They discussed at CitCon their desire to resolve the pop-in. They are actually using a similar things to Nanite, it was discussed a few pages back of this thread

however note that Nanite wouldn't actually work in scale of SC for any game on UE5 either because you would have a base 2TB game size which isn't realistically feasible.
However they are updating the render pass to do what nanite does but using Nvidia white paper to do a similar thing. They will do the GPU render pass, it check culling initially so it can calculate what it renders based on camera angle, kinda like how things check for screen-space reflections and thus they are not rendering what can't be seen and then you are just cluster swapping LODs from level 1 to 7. It basically culls enough triangles to make higher LODs closer to you not eat the total render budget. Now they say they are LOD-less because you are actually creating the different LOD models yourself, you are setting parameters that on the fly to control the LOD so Nanite as such has the ability to have 1000 LOD levels or whatever and it can cull the triangles at all those levels depending on how far from the camera the object is basically.
But yeah it being worked on and hopefully resolved. The second version of the engine video had cleaned up a lot of the pop & stutter.