Back in March of this year, Activision revealed to Polygon that alongside Mark Rubins departure, Todd Alderman joined Infinity Ward as Multiplayer Project Director. Alderman was part of the original Infinity Ward Zampella-era team that departed during the law suit back in 2010. Alderman departed along with Zampella and worked for Respawn. He then left Respawn as well and joined Riot Games.
However in February of this year, Alderman came back to Infinity Ward as Multiplayer Project Director, even stating that he never expected to be able to come back. But, according to his Linkedln page, he only worked at Infinity Ward for 4 months. He left in May 2015, and as of June 2015, hes back at Respawn as the Lead Multiplayer Designer. Its unclear as to why he decided to depart Infinity Ward so quickly.
Activision made a big deal out of his hiring back in March.