Successful ETL Automation: Libraries, Review papers, Use Cases
I don't think you'll find anything that checks all of your requirements, but here are some things to look at:


Automated ETL mapping: There is a tool called Karma started by a team at USC's Information Sciences Institute. It learns from your ETL mappings and helps automate future mappings. It's the only open source tool I'm aware of that helps automate the ETL process, but I would be very interested if there are others out there.
Large scale ETL: There are many many tools you could look at for the scalability you are looking for. I can personally recommend looking at Storm and Spark. Storm is excellent for stringing a connection of processing steps together that, given enough resources, can compute in near real time on streaming data. Not too dissimilar Spark has a streaming component with a similar use case, but standard Spark may fit your needs better if the data you are needing to ETL is a fixed set to be processed once.
Data storage: You may also need to consider where all this data will live during the ETL lifetime. You may need something like Kafka to deal with large streams of data. Or maybe HDFS to store a static collection of files.