If there are 4 billion NEM and 1 Billion NXT so the real value of NEMStake today or by launch time should be 1b/4b = 250,000 NXT
This is just in case that NEM is as good and as functional as NXT.
In reality NEM is in fact much richer than NXT in many ways "if you disagree its your own problem go do your own research".
So The equation should out stand 1 billion / 4 billion, and in return 1 NEMstake should be > 250,000 NXT.
In few days we will totally forget about NEMstake <-> NXT exchange and we will start to get more familiar with NEM <-> BTC exchange.
In this case 1 NEM should be at least = (1NXT->BTC)/4 =~ 0.00005/4 = 0.0000125 BTC
But there will probably be 8,999,999,999 NEM, as previously discussed