For face generation, I think there are deep neural networks that can generate multiple views of the same face [1], [2]. Stable diffusion already provides the possibility to generate variations. So I don't think it is a stretch to imagine that these existing capabilities will only get better and/or be applied to SD.

[1]: Multi-View 3D Face Reconstruction with Deep Recurrent Neural Networks [2]: Deep Neural Network Augmentation: Generating Faces for Affect Analysis