The quote from here: The Google Blog post
But despite these wins, and numerous
loyal fans, Wave has not seen the user adoption we would have liked. We
don’t plan to continue developing Wave as a standalone product, but we
will maintain the site at least through the end of the year and extend
the technology for use in other Google projects. The central parts of
the code, as well as the protocols that have driven many of Wave’s
innovations, like drag-and-drop and character-by-character live typing,
are already available as open source, so customers and partners can
continue the innovation we began. In addition, we will work on tools so
that users can easily “liberate” their content from Wave.
But I feel it will come back soon as something more adopted to real world needs, because the idea was grate!