Windows 7 can be expected to have huge improvements, on the accessibility front.  You can read the official post here, on the accessibility features with Windows 7.

In summary:

• UI Automation framework introduced with Windows Vista, has been greatly improved.  Now, the UI Automation and the legacy Microsoft Active Accessibility (MSAA) system combine together with a nomenclature of Windows Automation API
• Windows Automation API enables easy development of applications, that focus on accessibility
• Windows 7 will also have more accessibility utilities, out-of-the-box.  Also the existing On-Screen Keyboard and Magnifier utilities will be enhanced
• UI Accessibility Checker (AccChecker for short) and UI Automation Verify (UIA Verify) utilities, that are developed by the Windows 7 team, will be handy for developers to validate their applications and identify Accessibility problems, to eliminate them.  This will help to greatly improve the quality of accessibility utilities and make them compatible with the current and future tools based on Windows API

So, both the developers and end users can expect improved Accessibility features with Windows 7.

Microsoft, earlier in 2008 has announced that Windows 7, a much needed successor for the troubled Windows Vista, will be released in early 2010.

But, Don Reisinger of CNET News thinks otherwise. In his recent post, he discusses why Windows 7 might hit the shelves in 2009. In a similar note, Microsoft is working hard on making Windows 7 much lighter than Vista, particularly targeting the growing Netbook market and as an alternative to Linux.