As a traditional infrastructure/ops guy turned DevOps/cloud guy, I agree with your point that some traditional infrastructure/ops folks will struggle with the transition.
To those infrastructure/ops folks who are worried about cloud replacing their job, I would have them consider the implications of your main points.
1) AWS is a massive ecosystem
2) Understanding a service's use-cases.
3) Cost is really hard
Most Devs would love nothing more than to not concern themselves with the ins and outs of AWS so they can focus on building software (yes, I'm making a gross generalization here.) So, becoming someone who does understand the ins and outs of AWS almost assures a seat at the table.
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As a traditional infrastructure/ops guy turned DevOps/cloud guy, I agree with your point that some traditional infrastructure/ops folks will struggle with the transition.
To those infrastructure/ops folks who are worried about cloud replacing their job, I would have them consider the implications of your main points.
1) AWS is a massive ecosystem
2) Understanding a service's use-cases.
3) Cost is really hard
Most Devs would love nothing more than to not concern themselves with the ins and outs of AWS so they can focus on building software (yes, I'm making a gross generalization here.) So, becoming someone who does understand the ins and outs of AWS almost assures a seat at the table.