Good news! The limit for Pokemon Storage has been expanded to 2,000! The previous limit was 1,500, upgraded when Generation 3 was released. Each space upgrade costs 200 coins and will give you 50 spaces. To fully upgrade your storage from 1500 to 200, it will cost you 2,000 coins.
This upgrade arrives just in time for the recently announced Special Community Day and for the Generation 4 waves.