Here's the official announcement provided to developers today...
The iAd App Network will be discontinued as of June 30, 2016. Although we are no longer accepting new apps into the network, advertising campaigns may continue to run and you can still earn advertising revenue until June 30. If you’d like to continue promoting your apps through iAd until then, you can create a campaign using iAd Workbench. We will continue to keep you updated, but if you have any questions, contact us.
The news comes as recent reports have suggested that Apple is planning to disband its iAd sales team and move to a more automated platform.
We'll let you know when more details about Apple's plans become available. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.