Why do you want to use Hadoop? It might sound like a weird question but do consider it?
ES-Hadoop is useful when the data is in Hadoop and you try to get it into ES. Or you have a computational grid like Spark where you crunch numbers and need to tap into the data in ES.
By using logstash, it looks like you already have the means to move data from your source to Elasticsearch. So why go through Hadoop?
Note that involving a different system means allocating the necessary resources. Your 50TB would have to sit in Hadoop (until being consumed) and in Elasticsearch. Plus the network and CPU overhead to move them across to HDFS and then to Elasticsearch.