Are the replacement satellites for Iridium going to provide surveillance coverage?
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.