There are times, when discussing HTML, that XHTML enters the discussions. A lot of clients have expressed confused ideas when it comes to XHTML.
There are two reasons for the development of XHTML. The first is clean up, and remove, vestigial code. As HTML developed a lot of standards and code snipets were proposed, some never got off the launch pad, some were developed and died on the vine and others remained and are in existence today. XHTML is a new standard that will better organize the standards and remove unwanted code.
The second reason, and one that excites developers, is the ability for each developer, each company to extend the language as needed. In affect XTHML promises two seemingly contradictory goals. The first is that it would remove the dead weight of past mistakes and second it would allow each developer, each organization to make its own code - and hence their own mistakes; their own dead weight of no longer needed code. Of course, that means that each developer, each organization, can also keep their code libraries in order and up-to-date.
What does it mean to you the business user? Nothing at all. If XHTML is adopted as a standard your organization’s existing code will still work. It would mean that the next time one does a site redesign the developers would start incorporating XHTML elements. This is a coding issue and is something that should not be a concern to the business user anymore than any other coding issue. It will be years before XHTML becomes a standard and more years after that before your site becomes "unusable." For all we know XHTML will never be adopted.