I agree with @codinghorror to some degree. As far as the coming-to-market-soon future is concerned, slightly larger phones and tablets will become the norm for online communication.
Productive work, however, this won’t be. Virtual keyboards incur a significant sacrifice in terms of screen area and don’t come close to the precision of physical keyboards. But does this affect forums? Maybe. Depends on the purpose of the forum. I can’t see anyone typing up a full featured Howto here on meta on a tablet; all the puctuation in Linux commandlines, Ruby code and Markdown would make the prospect a nightmare.
But we’re allowed to dream… it’s just hard to draw a line between realistic, achievable-within-our-lifetime technology, and good old science-fiction. Personally, my wild, wild guess is that our grandkids will know stationary computers only from museums; their computers will be tablets, their walls and windows will become monitors, and their tables become virtual keyboards. A productive work environment wherever you choose to plop down your tablet.
And after that? Well…