Comment (including rationale for any proposed change):
The concept of baselines is misleading. One could define "AVI, TXT" as a valid baseline to tell his/her video collection "conform to WCAG 2.0" and can communicate the site as "accessible". To me this is senseless.
If there is a baseline, there should be a minimal requirement, at least for "HTML".
The conformance section of WCAG2 has been completely rewritten. The term "baseline" has been replaced by "accessibility-supported Web technologies". The issue of what it means to be an accessibility-supported Web technology is addressed in the section "Accessibility Support of Web Technologies" at http://www.w3.org/TR/2007/WD-WCAG20-20070517/#accessibility-support .
WCAG 2.0 is technology neutral, so it would be inappropriate to require any specific technology, such as HTML. (We would, nevertheless, be surprised to find environments that did not consider HTML to be accessibility supported).
If a Web page relies on nothing but AVI and text, it would still need to satisfy all the WCAG success criteria for the level of conformance claimed.