SpaceX has announced a launch target of May 2019 for the first group of operational Starlink satellites. SpaceX needs to launch about 2200 Starlink satellites by April 2024 to be in compliance with the FCC license. SpaceX filed with the FCC to modify its Ku/Ka-band NGSO license to relocate satellites previously authorized to operate at a lower altitude of 550 km and to make other changes. Here is a link to SpaceX’s 83 page technical report with its filing. The first generation of SpaceX Starlink satellites will have a simplified design for faster development and deployment.
There will be continuous improvement and addition of features in subsequent generations. Initial deployment of 1,584 satellites operating at 550 km with 25 degrees minimum earth station elevation angle. Insertion altitude for the modified satellites will be 300-350 km (depending on solar activity). This will require less fuel for orbit raising.