With all the recent conversations in the media about e-mail, I think the proper way to look at e-mail is that it will not go away or die anytime soon but it will "age out" as demographics within the workplace change and people become generally more comfortable with other communication and collaboration models.
I think that as people socialize, share information and collaboration in "spaces" (Facebook, SharePoint, Domino, etc) and also have more real-time / near-time communication tools (e.g., instant messaging, VoIP, XML feeds), the reliance on e-mail as the killer Collaboration 1.0 tool will incrementally diminish over time (I'm talking years and years).
TV was supposed to be the death of radio. Video stores were meant to sound the death knell for cinema. In both cases the old media re-invented themselves and reinvigorated their product in the face of competition. Vast multi-screen movie theatres offered the choice, comfort and convenience customers wanted. And with the Internet, radio has boomed to fill a host of niche markets and deliver them to a global audience.
Like radio and cinema, I believe email will shift and adapt in the face of competing collaboration tools to enable it to refocus on its core strengths. Nothing beats email as an asynchronous fire-and-forget communications mechanism. And for one-time ad-hoc collaboration the emerging technologies still have a long way to go.
So, I agree with Mike up to a point. I expect the focus on email as a collaboration tool to diminish, but I also expect it to be reinvigorated as a communications tool.