"The Rise Of The Cloud Administrator" Article
There's still a place for Sys Admins and Network Admins even in cloud platforms like AWS. Same thing with security admins. Small companies though still have multi-purpose admins though who have to do everything (systems, networks, security).
For me the big change in cloud platforms is the introduction of automated infratructures using tools like Chef, Puppet and CloudFormation. Environments can be created easily, torn down (or not) and management (costs, patching, security, control) is much more complicated.