It will be interesting to see what happens to the price of ppt when you cannot buy it in an exchange anymore.  At some point once the system is live all the ppt will be moved to the populous platform to buy invoices.  This is when I believe we will start to see the price movements.  I foresee a huge premium to buy these tokens if Populous can deliver on the invoices to buy.  Why sell when you are earning a passive income?  You would have to pay a huge premium to pry ppt from my wallet.  Of course this all depends on populous delivering on their end.