Also agreed. To whatever extent it's helpful, this is my take on it:

  Elasticsearch:
  * Data streams -- an abstraction that eases management of a set of indices containing time series data.
  * Wildcard data type -- makes searching for partial strings much more efficient
  * EQL -- a new query language that's popular in the SIEM (security info and event mgmt) world
  * Miscellaneous new aggregations
  * Tableau connector for Elasticsearch

  Other parts of the stack:
  * free version of Workplace Search (index all your stuff from multiple sources such as Gmail, Google Drive, MS Sharepoint, Salesforce, etc.)
  * free version of endpoint security from Elastic's acquisition of Endgame
  * Ingest Manager/Elastic Agent -- centrally manage and configure Beats-based endpoint agents that push metrics, monitoring, etc. to Elasticsearch
  * new rendering engine in Kibana