During the Multimedia panel at DrupalCon I elaborated on my plan for a single image module to rule them all in Drupal 6 and eventually Drupal 7. The plan is as follows:
1. Merge image.module and imagefield.module into a single CCK based module (so much more imagefield than image)
2. Provide an upgrade path for current users of image.module to the new CCK based image module
3. Merge the functionality of imagecache into image.module, again providing an upgrade path for users of 1.x image module. The image manipulation abilities of imagecache get merged in and should replace the current settings for image thumbnails. It's likely that the method for cron-generating of images will be maintained, but complemented by the on-the-fly generation of images provided by imagecache.
Then to make this "unified" image module part of Drupal 7:
4. Get CCK in core ;)
5. Move the image manipulation abilities of imagecache to image.inc, to provide a central framework for manipulation without image module.
6. Open a core issue and start continue the discussion there.
This issue has been discussed with walkah, dopry, and drewish. I plan to take the lead on implementation, though help will be greatly appreciated once the ball gets rolling on this herculean task.