I did not see this coming, but with the arrival of Gomes and Denis Suarez it's not very surprising. I'd be sad to see him leave, but I would understand if he does consider it. Our midfield is crowded now, and he's too good to warm the bench all season, but probably not good enough to make a place for himself as the primary rotation midfielder, let alone a starter. He could get many more minutes and develop more quickly elsewhere.
Rafinha is an attacking player and I have no problem with him not playing or competing for the CM role. I'd love to see him as Iniesta's primary backup, and Gomes as Rakitić's, but still that leaves Arda, a big name signing that would probably get the nod ahead of him, and Denis Suarez. (I'm not sure what role Lucho has planned for Denis, though.)
Unless Lucho is planning to use Denis and Arda on the wings exclusively, which he probably isn't, Rafinha will have a hard time getting minutes.