People often ask me about new trends beyond simply product roadmaps and flashy functionality. Like everything else in enterprise software, portals are indeed evolving.
I was recently prompted by a short but interesting perspective by David Sacks, covering a brief history of the public portal landscape and offering his take on its evolution. At first glance it's fundamentally a discussion of social software or consumer portals, but remember that enterprise portals, unlike other software segments (e.g., WCM), did indeed start out with a consumer focus (think: AOL, Yahoo!). And for better or worse, many employees come to enterprise portals from the perspective of their experience on large public portals.
According to Sacks the market has moved from a focus on browsing, then to searching (e.g., Google), and now to sharing (e.g., Facebook). I don't yet see that more contemporary notions of sharing have really penetrated the enterprise portals market, but it is certainly beginning to impact the enterprise software market, with IBM moving Web 2.0 to Center Stage or BEA Web 2.0.
Social information and interaction may very well move onto enterprise portal products in the near term, but remember that much of what the vendors have released so far is mainly consulting offerings and packaged prototypes. If you're looking to create Enterprise Portal 2.0, you'll most likely be an early adopter, so I'll urge you to start small and go for something with high impact, but low risk.