How many Ether exist during POW and then POS? Is it unlimited inflation?
72 Million coins from the crowd sale / dev fund. Estimated around 18 million coins mined prior to the move to POS (its estimated because we do not know the POS date yet but likely Q4 2016).
So around 90 million coins around the time of POS.
When POS starts, there will likely still be some small amount of continued inflation, but there are no details yet and it will likely be significantly less than the current POW mining rate.