Based on my initial research, it looks like only UTexture2D objects actually stream and load mips independently. Also, UTextureCube (through FTextureCubeResource) appears to load all mips at initialization.
I would really appreciate if Epic Staff would confirm my findings or point me to where I went awry.
If confirmed, can you explain why UTextureCube is not streaming and loading mips independently?
Is there anything preventing the inclusion of much of UTexture2D into the UTextureCube tech?