The blog post about accessibility updates is a step in the right direction. There is more information there than has been previously available about the updates being made. The information is still broad and vague, however, and appears to be inconsistent in some places. For example, it states that "Interactive elements performing page actions will be marked up with <button> tags." What exactly constitutes "page actions" is not defined. It also states that "Navigational elements will be correctly labeled using <a> tags." but later indicates that "All interactive elements—like “Next” and “Previous” buttons—will be fully operable using only a keyboard."
So are Next and Previous navigational items which will use <a> tags, or is navigating to the next or previous part of a module considered a "page action" and so these will be <button> elements?
Please expand on the work you started with the blog post and provide additional detail about specific parts of the user interface that are changing.