Considering how there is currently a thread on this forum about how a Platinum feels his status is useless, I would tell your friend to wait in the pity party line.
And then I would tell him to read the forums of the other carriers, and see the upgrade percentage of higher level elites. The grass may seem greener, but I think if he decides to defect elsewhere, he's going to be the same boat, except he will forego some of the other benefits I see of CO - like, IME, cancelling the least amount of flights for mechanical reasons (US is notoriously guilty of this), having wonder FA's and CSR's, better fleet, etc.
Flying today isn't like how it was 20 years ago, when 25k annually earned you something and designated you as as serious FF. Sadly, silver tier is almost leisure status, considering how many miles are logged by top tier elites.