Guild Wars Nightfall

Chapter Three is an upcoming stand-alone product ("Campaign") of the Guild Wars game series, a follow-up of Guild Wars Factions (Chapter Two).

No title has been announced so far.

Content
Nothing is known about a theme or new content so far.

Release Date
No release date has been officially announced.

However, keep in mind these two stements by ANet:
 * According to Jeff Strain Chapter Three has been in development since Nov 2005 (source) and the development time for each campaign is roughly 1 year.
 * ANet have stated that they plan to release two campaigns per year. Factions is due for release April 28, 2006.

Based on this, the campaign should be out within a year from the release of Factions. Keep in mind that long-term target release dates in the gaming industry are often optimistic and tend to slip backwards.