[DISCUSSION] 2026 Q3-Q4 Roadmap Discussion

- part of https://github.com/apache/datafusion/issues/21036

DataFusion is cranking out features and releases, even as the community grows (the 54 release had [139 contributors](https://github.com/apache/datafusion/blob/main/dev/changelog/54.0.0.md)!)

It is still mind boggling 🤯 to me that the project moves along without a central planning authority. However, the decentralized model seems to be working well and I see no reason to change it.

The lack of a central authority **DOES** mean we have to make an extra effort to coordinate, and to do so we have a history of doing a public roadmap discussions (see past list on https://github.com/apache/datafusion/issues/21036), most recently by @adp2201 in https://github.com/apache/datafusion/discussions/21017 🙏 )

These discussions typically serve to
1. Communicate what maintainers plan to work on / what they view as important
2. Help would-be contributors find areas that are likely to get maintainer attention (and thus faster reviews)
3. Give a forum for community members to articulate their priorities (and maybe find maintainers that share the priorities)

Thus, I hope this ticket will foster a new new discussion for the remainder of 2026 and see what people are going to build next!

Read dev/changelog/54.0.0.md for recent project context, then review issue #21036 and discussion #21017 for prior roadmap discussions. Add priorities or planned work for the 2026 Q3-Q4 roadmap in this thread; done means the relevant goals and areas are clearly recorded for contributors and maintainers.

Written by the indexing model from the issue text.