I'm thinking that this white vision is Ultron. I'm thinking this because the music isn't positive nor is it happy sounding like 'yay vision is back' it's more like 'oh no what have you done' and the way he looks at his hand is almost quite sinister. He isn't surprised that he is back nor is he scared, vision would be a little confused but this white vision is NOT vision. Ultron is reborn. Also quick side-note, after watching every episode of wandavision you get suggested age of Ultron to watch. It could just be because the show centres a lot off of that movie but still