Based on my (limited) knowledge of ElasticSearch, it appears that it is a search server that would work in conjunction with the database and is used primarily to search and index document files.
If this is correct, I don't think that NuoDB would be a replacement for ElasticSearch but could likely work in conjunciton with it similar to PostgreSQL.
Also, similar to Volt, NuoDB doesn't have full-text-indexing functionality.