OpenSearch really appears to have a significant amount of development momentum. It is functionally equivalent with Elasticsearch. There would be no incentive for AWS to do this. After ES broke their compatibility with OpenSearch they also broke compatibility with their own older versions. This forced users to choose in order to move forward with anything. I don’t know how it worked out for others but I’ve converted hundreds of ES clusters to OS and switched all development to OpenSearch because they started gaining momentum and didn’t make decisions that were actively hostile to their users.

Edit: As long as OpenSearch doesn’t start breaking the self hosted use case, I don’t see any reason to consider Elasticsearch again. In fact, ES would have to offer up a significant advantage to overcome the bother.