User blog comment:WikiaIvan1997/Ike's new voice actor/@comment-4417828-20141027170410

All of Ike's voice roles have gone to the children of the staff. Most of the later episodes use voice samples from previous recording sessions instead of getting new voice overdubs. The episode "Taming Strange" from last year might have been a behind the scenes joke on all of the children who played Ike have grown up. It is very rare of South Park Studios to hire a new actors for roles, so this is not a real possibility. Besides all of that, Ike is not a central character.