It will come down to explaining (I'm assuming he pleads guilty) when the substance came into his system. Having had experience (on the good guys side), can assume the sample will be tested to find the levels. All people metabolise things differently, but it should be able to give a ballpark figure of when it was ingested.
Then the games begin. Does he come completely clean, eg has a habit or is an occasional user. Or did a mate slip it into his drink.
Depending on a lot of things, I can see it being months not years, maybe since it was virtually the end of the season they might make it long enough to stretch into a portion of next season, not sure where he goes in our offseason typically, but that would be lengthy enough. And since he's a star, I can see Sydney definitely keeping him, albeit with him doing extra community engagement to make amends. The suspension needs to be enough of a deterrent but not crushing, especially since it was more than likely recreational than performance enhancing.
It does set a double standard, if he was a mid level to DP player, could be career ending. If Sydney do rip up the contract, if the Buford rumours are correct, then Brisbane would be logical destination.
But can't see it being a quick process, Peter Bol took 6 months but that was an entirely different situation.
Drugs do ruin lives, but in this case he's a user not a dealer (hopefully), so smack on the wrist, remind players not to do lines during the season and move on. Could well cost him a million dollars at the end of the day, a lot more than most would be penalised. And will follow him around especially in the short term, maybe even leading to not making boomers in years to come just because of the stigma.
And if some people think he's the only one that's done it or doing it are dreaming.