Google has thrown in the towel with Wave. Ars Technica has the details in their Post: 
Wave cancellation: Google gives up on next-gen messaging platform
Twitter is closer to that Next-Generation Messaging Platform than Wave ever was. The heavyweight browser dependency and lack of a desktop app was a significant drawback. Even more of a death knell was the lack of accessibility from mobile clients. The reason Twitter wins as a game changing communications platform is that it is accessible from just about anywhere. Even a lowly cell phone with just SMS can interact with Twitter. A simple API enabled desktop apps, browser add-ons and mobile clients to be created. The API accessibility also meant that Twitter could be extended through links to other products - multimedia, web site links. People are continually finding ways to extend the usefulness of Twitter by integrating with other services.
I am sure the core elements of Wave will not be wasted. Elements will probably pop up in Google Me, or whatever Google calls their Facebook competitor.
Google, just remember one thing. Don't get caught up in the religious wars of HTML5 web-based apps. There are still many users out there that don't have HTML5 capable systems. Openness and accessibility from multiple platforms will be an essential part of competing with Facebook. Your services need to be available where ever your users are. On whatever platform they want to access from. This was never the case with Wave. I know, I tried Wave with Safari. I would forget to load the page and get past the warning messages. I even tried creating a Fluid app so it could be a separate application. But if I couldn't pull my feeds in to the environment then it rapidly became a novelty.
Email integration, access to and from my preferred IM platform, RSS Feeds, Easy hyperlinking and embedding. These are all the things that Son of Wave needs to deliver if Google hopes to compete with Facebook. Let me pull and push content from the places I already frequent, like my email client, my IM, my phone. Make embedding easy so I can easily get sucked in to the product. Make security integration easy while you are at it.
Farewell Google Wave!
You were a fascinating experiment. Google, learn the lessons well. Don't forget your roots. Look at what has succeeded on the Internet. Simple and Easy has invariably beaten out Sophisticated and Complex. REST beating SOAP is just one example. Look how your millions of users have mastered embedding a few lines of javascript or an embedded url in order to take advantage of your products. That is the lesson that Wave ignored and it cost the product dearly in the end.
