Read these posts:
- Are you prepared for web 2.0 programming?
- anchor tag inside an iframe
- Modern web browsers, accessibility and usability.
With technologies like iframes and AJAX, web applications become more and more like desktop applications. You get rid of the page load. Pages are no longer unique. That makes obvious problems for SE Bots. Indexing sites and static text pages will therefore, most probably, be relatively more important in the future.
Technologies like XPath that is a query language on the DOM tree (dome nodes) is today an important part of the XML technologies. With scripting languages like JS and PHP you can manipulate these nodes dynamically. You may even deliver JS code by PHP from a MySQL database to insert, move and delete elements from the HTML inheritance tree or more generally, from the XML DOM tree. Moving pictures from picture nodes and you have a movie.
Idea (question): Do we already see a tendency that the next generation web browsers will develop more into web operating system, where XML coded pages will be parsed as a RSS reader parses them today? Modern web browsers have already integrated RSS functionality into the software.
Together these different technologies may merge into an overall technology interpreted by tomorrows browsers that make web applications more and more like desktop applications.