So, let me extrapolate

Our goal is free Dash and infinite masternodes.
free DASH 5600-3900 : 2700
locked in masternode 3900
In free dash(2700) many dash would be hacked or out of handlling, forget wallet password....
So I think free dash is small.
Let's think : effective dash amount are about 4000*1000 coins
( free dash in exchange site in ask side are 78*1000 coins )
( Poloniex dash lending are 16*1000 coins )

After oct 2015, linear increasing in MNs
: Mined coins,masternode reward coins goes to new masternode.