At the same time though, support for WebSockets in major browsers is woefully little, with only Chrome currently supporting it in an active "release," and (I believe) support available in the Firefox trunk for a later version. This still doesn't account for Safari or Internet Explorer, the latter being the biggest impediment to adoption.
Additionally, I certainly don't think this is the beginning of the end for "AJAX" — not in the least. AJAX still has very strong grounds in pulling down data from the server that doesn't require some sort of long-running communication.
Yes, let's get excited, but a little bit of a sanity check should be done if you're ready to call AJAX "dead" (or "dying").