I think they said there would be but wasn't implemented in the demo.
It is implemented, but not rolled out. They're working on ways to make it less noisy and give you more control. Part of it is learning how to use what is available already. The search functionality helps a lot.
You can create 'folders' which are live saved searches.
Also, the source to the Wave Federation Server was released, so at some point, people will build other clients (they include a command-line client, and an Emacs client was shown in the demo), so if you want a more IM like experience, someone might do it, or if you want something that looks like Outlook, that can be done to.
The Wave web client is the most visible and noticeable part of Wave, but like Email, it's more about the underlying protocols (e.g. IMAP/SMTP). Wave supports a cryptographically secure federation protocol, which means an end to anonymous spam, for example.
I would consider the current Web client an experiment in UI design. They don't know if it is the best way to view and organize waves that's why they have rolled out a large scale beta to get feedback before productization.