Croatia in Schengen Zone - when?

Mid 2016 was the last date I heard. though all these refugees / migrants passing through Croatia will almost certainly cause a delay. The existing Schengen countries bordering Croatia (Hungary, Slovenia) will almost certainly veto opening the border to Croatia if there is any risk of the refugees currently in Croatia moving north through that open border.
Bulgaria and Romania have been due to join for years, but it keeps getting postponed because of their porous border controls.

Not in the foreseeable future. First they need to pass all the technical inspections and then the migrant crisis needs to calm down for any talk of Schengen expansion to even begin. I really wouldn't count on it until at least 2018 in the best case scenario.