(And not just the smells of summer)
When the luminaries of an industry are all out on the hustings evangelising change, and by change I'm talking about stuff that no one has tools or methodologies for yet, then it's fairly obvious things are in a state of flux.
This change can probably be best described as the son of Ajax. The amusing thing with the explosion of Ajax was that it wasn't anything particularly new, most of the underlying technologies had been in place for the best part of a decade. What Jesse James Garret did when he launched the Ajax meme was give us the lexicon to talk about the changes we were witnessing with Google Maps and GMail.
This new revolution is going to change everything because the web browser is going to become host to complete applications, and the back end is going to become nothing more than a persistent communications hub for people to interact through. This changes the performance requirements of the back end, away from relational databases and towards appengine style distributed datastores.
The new capability that this gives customers is the ability to use the webapp from a disconnected client. This might not seem like a big thing, until you take into consideration the explosion in sub notebook computing devices, netbooks, iphones and androids, all of which are partially connected to the net through the 3G telephone network and the occasional WiFi hotspot.
This new capability is going to be a huge driver, and it requires a complete rethink of how we build web applications.