They won't make it a casino or something, they don't want to appear to be encouraging children to gamble..
Ideally (in my own head) it would be something simple like a chest where you put gp into. You then have a 50% chance of doubling that money, and a 50% chance of it disappearing. This would probably take some gold out of the game and help with inflation.
Knowing Jagex though they will do something with the current bh system and call it 'high risk fun" or some shit.