I'm at the Burton Group Catalyst Conference listening to a panel that includes representatives from Adobe, IBM, Mark Logic and Microsoft. One of the questions was about "what goes away" as we add more tools and newer technologies (e.g., social software). I thought someone would talk about the demise of e-mail but not surprisingly neither IBM or Microsoft pushed the issue that one of their key revenue generators would go the way of the fax machine...
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).
Could there be an e-Mail 2.0? Sure - unfortunately I don't believe that either IBM or Microsoft will significantly restructure their respective products in a transformational manner. But we are seeing some interesting combination of e-mail with XML syndication to insert a level of abstraction between sender and receiver.