According to Latnio Review's sources, a new casting call is circulating throughout Hollywood for this upcoming sequel, with Marvel and Disney seeking a 'Physically Imposing Caucasian Man' between the ages of 40-50 for this supporting role.
In the Marvel comic books, Baron Von Strucker is a leader of Hydra, and a known enemy of S.H.I.E.L.D. and The Avengers. He is both ageless, and has the ability to die over and over again, always coming back for more. In Joss Whedon's current draft of the script, brother and sister duo Quicksilver (Aaron Taylor-Johnson) and Scarlet Witch (Elizabeth Olsen) work for Strucker. It is not known if they are part of Hydra or the Masters of Evil organization, but El Mayimbe suggests that it is Hydra, as it was previously set up in Captain America: The First Avenger.
Right now, Marvel is believed to be eyeing two actors for the part. Marton Csokas and Dougray Scott (who was originally cast as Wolverine before having to turn the role over to Hugh Jackman due to his contractual obligations on Mission: Impossible 2) have reportedly both been approached. This does not mean an offer has been made, or that they are even still being considered. But both actors do fit the needed requirements.
Marvel has not commented about this news, and it's unlikely that we'll hear a confirmation about Baron Von Strucker being in Avengers: Age of Ultron until sometime after the new year.
Avengers: Age of Ultron comes to theaters May 1st, 2015 and stars Chris Hemsworth, Jeremy Renner, Robert Downey Jr., Scarlett Johansson, Chris Evans, Samuel L. Jackson, Cobie Smulders, Mark Ruffalo. The film is directed by Joss Whedon.