You mean he wouldn't want to be a bit-torrent?seeing as some people are inevitably going to start worrying about this, lets look at it logically.
he is staying within the CFG, so we can pretty much bring him back at any time if need be.
pep will have given his blessing - torrent wont have wanted to be an assistant forever - hence recruiting arteta to replace him.
this will give arteta more responsibility with a view to him potentially taking over from Pep.