It would be good to know what some of these new features will be and why I (as a redmine user) should care.
After a quick look around, here is the "why" behind the "what":
https://www.chiliproject.org/projects/chiliproject/wiki/Why_...
Reasons for using ChiliProject instead of Redmine:
https://www.chiliproject.org/projects/chiliproject/wiki/FAQ
It appears that the driving factor was one of centralization vs decentralization. Some of the developers wanted more openness with regard to contribution.
Eric has written a lot about redmine and does consultancy about it so I guess that after investing so much on redmine, the only option left for him was to fork it.
I've been planning on offering redmine as Saas for a while at http://redmined.com (yeah, there's a lot of people doing the same already, I know) but maybe I'll move to chiliproject if the fork goes well.
It should be suffice to say that both projects are going to continue to co-exist and probably going to be rather similar for quite some time. We don't want any bad blood between us and we are going to try to work together towards our common goal. We on the ChiliProject side just feel that more open and engaging development process helps the product and is more fun for all participants.
Feature-wise we try to make ChiliProject more modular and extensible by plugins and third-party tools (via the REST API). Also, we plan a deep UI/UX overhaul and having more flexible workflows and permissions. The exact roadmap is still to be defined (in an open community process), but I think you get an idea.
The first release will be compatible to Redmine 1.0.5, and we try to keep the migration path between Redmine and ChiliProject open as long as possible.