I'd like some actual comformation on this, because unless my brain has lost its capacity to distinguish real from CG this totally looks live-action. Again I'll point to the eye reflection that clearly shows the face scanning rig - this thing...
If these were fully rendered, fully finished faces that they wanted to use in this teaser, why would they keep that obvious refelection in the eyes? Because of the rig with light being shone at every angle of the face it looks a tad flat, but those faces are real. You look at Udo Kier's face - the way the nose moves along with the premaxilla, how the skin flares and bulges subtlely - no tech today can match that level of movement. Even the line they say in the trailer and Sophia Lillis' sudden scream are most likely information tests to get the widest range of expressions from the actors for the CG models and animation rigs. This also explains why each actor's hair is tied back, which is a standard when scanning a face.
I'll eat my words if this actually is CGI, but nothing from this trailer indicates it's anything other live-action test footage.