Never. They won't.
The only bots that will dissapear from the games are the poorly programmed ones. Sadly, those account for only 10% of the total amount of active bots. Probably.
It's been eight years now, and bots have been a problem since day one. Not once was there a bot free moment in WoW. We've had several dozens of "banwaves", but look; Go into a BG and notice how at least ~35% of the players are botting. Why? Well, why not? They won't get banned anyway.
Blizzard is not capable of stopping bots. I don't think any company is. All mmos are like this. What's the point of playing legitimately anymore? Its incredibly hard to keep up with something that is not able to tire, and perseveres through loss without any shred of emotion. A bot is the ultimate grinder. A legitimate player has NO chance of competing against it.
Whether its gold, honor, or experience, a bot will always be around the corner gathering all of that without suffering from any consequences. The botting will never stop. Not in Diablo 3, not in World of Warcraft. Nowhere. They are unstoppable. Especially for Blizzard.