If you look at the GitHub URL:
You'll see it's actually a Neo4J project. So, I believe it's more of when is Neo4J (or somebody in the Neo4J development community) is going to modify the project to support the latest Neo4J release.
It is a known issue. See:
One possibility to consider is to use Microsoft's Cosmos and Gremlin implementation if you really need Gremlin.
Unfortunately, this is the extent of my understanding (or conjecturing) of the situation. Sorry I can't be of more help.