Is there a firm or preliminary decision on which modules will leave Core for 8?
There is an issue report for that ([Meta] Make core maintainable), but nothing has been decided yet. As you can see, there are different opinions about what to remove, and what to keep.
catch, the latest maintainer added to Drupal 8, expressed his opinion on that; the same did Dries, chx, Crell, and eaton (just to cite some of them). There is an agreement about some of the modules to remove, but there isn't a complete agreement.

That issue report is not marked as postponed, and a new issue report has been opened (Establish heuristics for core feature evaluation).