We have quite a few tickets still flagged for 4.0 that aren't in keeping with the idea that the code is frozen:
https://issues.apache.org/jira/issues/?jql=project%20%3D%20cassandra%20and%20(fixversion%20%3D%204.0%20OR%20fixversion%20%3D%204.0.0)%20and%20resolution%20%3D%20unresolved%20and%20type%20in%20(%22New%20Feature%22%2C%20Improvement) I propose we move all new features and improvements to 4.0.x to keep the surface area of change for the major stable.
