Google Wave is declared dead, but it won't die fully until some time in 2011, Google confirmed in a post "While we're still working on plans, we do want to specifically call out that: Wave.google.com will be available at least through the end of the year. And, there will be ways to export your waves before the end of the year."(empahsis added)
And, that "we wanted to let you know that we've been hard at work figuring out all the details of the next steps. We're looking at ways to continue and extend Wave technology in other Google products, open sourcing more of our code and providing support for our loyal users and Apps customers."