I believe zerocoin is supposed to be implemented somewhere in 2017. I read somewhere that it's hard to make an exact guess as to when it will be implemented because Pivx will be the first PoS coin to have the zerocoin protocol implemented and it is not yet possible to estimate which bugs will arise and how much time it will take to overcome them, because it's all new. However, zerocoin implementation is a priority of the developers.

Once zerocoin gets implemented though we will probably see the price skyrocket. Pivx will be the most secure and private coin there is, it would surprise me if Pivx doesn't reach top-10 market cap after zerocoin implementation.