Amazon forked ElasticSearch into OpenSearch. When deciding which platform to go with (we are an AWS customer) I decided to stick with the company whose future depends on their search product (Elastic), not the one that could lose interest and walk away and suffer almost no consequences (AWS). If OpenSearch is still around in 5 years, and keeping pace with ElasticSearch, then maybe I'd consider it the next time I'm making this choice.

Also there's a lot more to ElasticSearch than full-text search (aggregations, lifecycle management, Kibana). Doesn't seem like Kendra is going to be a replacement for our use case.