Aaron Taylor-Johnson has been sighted on the Italian set for Avengers: Age of Ultron. Note the greyish-white hair, but NO GOOGLES! My thought is that they may explain his speed enhancements are some sort of super-soldier experiment gone wrong or time “phasing” that allows him to appear as though he is moving extremely fast. Either way, they are going to use science to try to explain it.
Jeremy Renner has also been spotted in Italy and it looks like there was some surreptitiousness associated with this picture.