This is a great news. I quote from the Amazon press release:
To make Kindle more useful for the blind, the Kindle team is currently working on an audible menuing system so blind and vision-impaired readers can easily navigate to books unassisted, in addition to listening to books as they can already do today with Read To Me. In addition, a new super size font will be added to Kindle, increasing the number of font sizes from six to seven. This seventh font size will be twice the height and width of the current largest font. These new features are scheduled for release by the summer of 2010.
Does this mean the TTS function will be available for all? Or will Amazon continue to let the publishers pick and choose what books they want to open the TTS to? If the latter happens, then nothing is really going to change.