There's a very serious risk that some or all of these princes are going to get executed. That's how Saudi Arabia does things. It's unlikely they will all be set free to go back to their old lives, it would pose too great of a risk to the new power structure MbS and the king are trying to put into place. For example it appears they're going to confiscate Al-Waleed bin Talal's assets. There's no chance he's going to be set free after this, to then go overseas and cause havoc for the regime.