Adding a requirement - backwards compatibility (not) (#730)

* Adding a requiement

* Moved the backwards compat to 2.3

* Terminology update

* Update requirements/index.html

requirements/index.html

@@ -128,6 +128,9 @@ <h4>Maintenance</h4>
 						<li><strong>Evolving Technology</strong>: WCAG 3.0 needs a flexible design that can be updated as new technologies emerge, assistive technologies improve, and changing technologies produce new barriers for people with disabilities. Accessibility guidance and all supporting documentation should anticipate common scenarios like new technology and the introduction of new modalities like surface reaction and ultrahaptics. As content technology evolves, it must be re-evaluated against assistive technology for compatibility. Likewise, as assistive technology evolves or emerges, it must be evaluated against the backward compatibility of various content technology.</li>
 						<li>
 							<strong>Governance</strong>: Utilize tools that allow interested parties to predict when issues important to them are being discussed. Maintain a backlog that reflects issues along with their status. </li>
+						<li>
+							<strong>Backwards compatibility</strong> The WCAG 3 guidelines will take a cautious approach to backwards compatibility to early versions of WCAG 3.  After the first publication of WCAG 3 guidance and conformance model the guidelines aim to be backwards compatible. However, it will not be bound to backwards compatibility if a substantially more accessible outcome can be achieved. Where there are backwards-incompatible changes, the changes will be highlighted in the supplementary materials so that users of the guidelines know exactly what has changed.
+						</li>
 					</ul>
 				</section>
 				<section id="opportunities_issue-severity">