I would be be pretty disappointed if we lost Oates, he is just a Bronco through an through and the fans just love him, but saying that I can understand if he took an opportunity to go somewhere that gives him a chance to play second row.
I think Sua is an investment in the future and is a must keep as is TPJ, unfortunately I agree that probably leaves Glenn as the fall guy assuming Gillett returns, which is also disappointing as Glenn he has been a great player for our club and just real decent bloke. Glenn is just one of those reliable guys you need who doesn't cost you a lot of money.
I would think if Bird was fit to play centre (with Kahu on the wing) then Oates would have been given a chance in the second row, unfortunately due to injuries to both Kahu and Bird that just hasn't happened, sadly it may just cost us Oates.