The truth is Dwarfpool has been a lot more stable than any of the other pools in my experience. If the other pools can keep the same uptime and offer similar features as Dwarf, then you might see more people spread out. Also I thought the risk of any kind of 51% attack was mitigated by POS? They would require a significant amount of the available coins (stake weight) in addition to controlling 51% of the network. Am I wrong?