There is nothing official to say he is on loan, and I've looked quite thoroughly. And by official I mean from Palmeiras, us, or any FA/FIFA/UEFA etc. The offical press release said "he will stay until January" not that he'll be on loan.
He's also not listed as being on loan on our official site, despite all our other loanees being listed. And while not the definitive authorities, both Football Manager and Wikipedia don't have him listed as on loan either.
Also he wouldn't be coming here for a medical as reported today if he was already our player.