If I no longer control a permanent when it would be sacrificed, is it still sacrificed?
The rules say:


  701.16a To sacrifice a permanent, its controller moves it from the battlefield directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent they don’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action.


(emphasis mine)

So in that case, your opponent will control Planar Chaos and it won't be sacrificed.