This is the latest in a series of notes from Facebook which show how seriously they are taking realtime. From their (I think excellent) response to all the negative feedback about the new redesign:
With the recent home page changes, we’re trying to present the right balance between what’s happening right now and what’s interesting over a longer period of time. We realize that both are important and getting them both right is crucial for the product to work. In the last few weeks, you’ve seen us shift the main emphasis towards real-time conversations and updates as the entry point to Facebook.
I think this says pretty clearly that they see the future as realtime.
Going off piste a bit, I also think that to do realtime well probably means that being linked and open to input from other web applications is important. The realtime data is much richer if I can see what everyone is doing right now whether they are on Facebook or not in a way that is less true for non-realtime updates. The most obvious case of this is keeping up to date with your buddies who use primarily use other social applications and only log in to Facebook every couple of days.
Thus we can expect them to keep pushing and extending Facebook Connect, supporting OpenID and making Facebook data available to third party applications.