EMR upgrade with AL2

Hello, Please refer the answers below,

1. What happened in case the upgrade not complete and can I access my cluster after the EOL?

Answer: Once the maintenance phase ends, the AMI 1 will no longer be supported and you will not receive any critical or important security updates. Older versions of the AMI and updated packages will continue to be available for launch in Amazon EC2 and for installation from the Amazon Linux AMI yum repository even after new Amazon Linux AMI versions are released. However, we encourage customers to move to, and to use, the latest version of the Amazon Linux AMI in order to ensure the best customer experience that we can provide.

2. Any suggestions to migrate hdfs data to higher version? 

Answer: Use Distcp or S3DistCp tool to achieve this. S3DistCp is similar to DistCp, but optimized to work with AWS, particularly Amazon S3. You can copy data across EMR clusters through EMRFS(which is strongly consistent). Here is the document for reference,

https://repost.aws/knowledge-center/copy-s3-hdfs-emr

https://aws.amazon.com/blogs/big-data/seven-tips-for-using-s3distcp-on-amazon-emr-to-move-data-efficiently-between-hdfs-and-amazon-s3/