Find some updated version about the current roadmap of the 7.x branch.
Release a beta
Release a stable
Get enough user feedback first.
Cleanup major issues:
Communication / Marketing / More docs
Update simplenews frontpage, release documentation
Take a short break... :-) (hopefully also other people get reactivated and join development again.)
Improve test coverage
Bugfixing and some smaller features
Those are subject to happen pretty soon. No architectural concerns, possibly subject of 7.x-1.x.
Push some module ports
http://drupal.org/project/simplenews_linkchecker (D7 dev available)
http://drupal.org/project/webform_simplenews (D7 dev available)
http://drupal.org/project/simplenews_scheduler (D7 port started)
Bigger features / rework
Those are pretty advanced. Possible subject of 7.x-2.x. However it no API change needed, they're also candidate for 7.x-1.x.