ElasticSearch provides most of the same benefits on top of Lucene, while adding other modern features such as:
Auto-scaling of data store indexes across multiple cpu nodes
Auto-sync of indexes when additional nodes are applied
Easy configuration and handling of multitenancy needs
Percolate feature which provides subscription type functionality
All metadata and indexes can be persisted across multiple nodes.
Provide a case for or against replacing Solr functionality with ElasticSearch.