Are the replacement satellites for Iridium going to provide surveillance coverage? Iridium satellites are to be replaced using SpaceX rockets.

Will the new LEO satellites be used for continuous tracking of commercial flights?
The next generation of Iridium satellites will have ADS-B receivers installed on them which will be used to track properly equipped aircraft. The company providing this service is Aireon.

Most airliners are already equipped with ADS-B transmitters. From 2020 it is manadatory on the USA and in Europe to have ADS-B. 

The first satellite were to be launched earlier this year, but so far nothing has been launched.