Solr is one of those technologies which works but isn't really glorious to use and is bit stuffy with its XML configurations and Java interfaces. It's a bit of shame, because search engines are so popular nowadays and everybody seems to be fixated on using ElasticSearch. Which from what I've read and heard is resource-hungry and not really cut for simple text-search.

Maybe someday somebody will create a new search engine that will be hipster and easy to use, like Algolia but open-source. I'm bit curious though how incumbent Lucene is as the core search engine that it would even make sense to try and recreate it in another language. Probably too much that unless somebody has money to throw around it will remain so to the far future.