Jon doesn't have a real physical addiction. He was clean during his fight so that means he didn't have any coke for a few days leading up to the fight. If he was physically addicted there would be no way he would of been able to make weight, go all the pre fight shit, or fight while going through withdrawals. The post fight interview was in no way withdrawals, not even close. I have no idea why people are bringing that up.
Of course mentally is a different story, and people can be mentally addicted to anything, even cheeseburgers. Honestly though since he isn't physically addicted and got caught this definitely should save him from any real addiction. He won't have any real symptoms of not using, just boredom which is easy to get over. Most people become mentally addicted without really knowing, and end up messing up by taking the drug too many days in a row which causes a real physically withdrawal addiction. That's when it's almost impossible to quit.
So in reality this actually a great thing for Jon. He gets a wake up call before his mental addiction, if he even has that, turns into a full blown addiction. This should be a cake walk for him considering he seems like a dude who's in a good place, just likes to party.
Rehab is a PR stunt.