What should, and should not, be added to the core in the future is always going to be a contentious issue.

I think the core should stay the core and not be a dumping ground for every possible feature anyone could ever want. It would also quickly become a nightmare for the core dev's to debug.

I think there would be great value continuing to develop the core api's and branch out major new functionality into Plugins. Two good existing examples of this are bbPress, and Jetpack.