Book 14, titled A Memory of Light, is currently scheduled to be released on January 8'th 2013. It will be the final book in the series.
Generally, for this series, Tor publishing has released the mass market paperback edition about a year after the hardcover release. If this holds true for book 14, the paperback edition should be released around January 2014.
Wheel of Fortune - 1983 14-135 was released on: USA: 14 March 1997
Wheel of Fortune - 1983 14-173 was released on: USA: 14 May 1997
Wheel of Fortune - 1983 14-31 was released on: USA: 14 October 1996
Wheel of Fortune - 1983 14-54 was released on: USA: 14 November 1996
Wheel of Fortune - 1983 14-92 was released on: USA: 14 January 1997
Wheel of Fortune - 1975 1988-06-14 was released on: USA: 14 June 1988
Wheel of Fortune - 1983 Wheel Into 1997 2 14-87 was released on: USA: 7 January 1997
Wheel of Fortune - 1983 Wheel Into 1997 4 14-89 was released on: USA: 9 January 1997
Wheel of Fortune - 1983 Wheel Into 1997 5 14-90 was released on: USA: 10 January 1997
Wheel of Fortune - 1983 Wheel Into 1997 3 14-88 was released on: USA: 8 January 1997
Wheel of Fortune - 1983 Wheel Watchers Club 14 - 23.194 was released on: USA: 8 June 2006