This page outlines certain goals, nothing is guaranteed to land in a specific release.

1.8 

Widget Factory

• full prototypal inheritance
• direct instantiation without calling an init method
• split destroy methods into revert and remove (remove can be much simpler)
• unit tests
• upgrade guide
• docs page

Button

• unit tests
• demos
• document buttonset

Consistency

• parameters that accept elements (http://gist.github.com/233531) 

1.9

A11y

• merge in Felix's jQuery RIA code
• add ARIA support to existing plugins
• high contrast mode (see comment on jQuery UI CSS Framework)

Widget Factory

• cross-window support
• ability to clone elements with initialized plugins?

Effects

• review and merge effects branch into trunk to get class animations working cross-browser
• figure out how to get full effects support into plugins #3772
  • implement in at least one plugin #2358

2.0

Plugin rewrites

• datepicker
• draggable
• droppable
•  

API Cleanup

• various existing and mostly complete widgets have API flaws the need compability breaks to be fixed, a 2.0 release could help with that
• eg. for the Accordion, as outlined on the Open Issues section
• migration should be easy, so where possible, deprecate old options for a few releases, and remove only later (months/years inbetween)