The Collaborative International Dictionary of English v.0.48:

Offing \Off"ing\ ([o^]f"[i^]ng; 115), n. [From Off.]
   That part of the sea at a good distance from the shore, or
   where there is deep water and no need of a pilot; also,
   distance from the shore; as, the ship had ten miles offing;
   we saw a ship in the offing.
   [1913 Webster]

   in the offing
   (a) coming; arriving in the foreseeable future.
   (b) visible but not nearby.
       [PJC]

WordNet (r) 3.0 (2006):

offing
    n 1: the near or foreseeable future; "there was a wedding in the
         offing"
    2: the part of the sea that can be seen from the shore and is
       beyond the anchoring area; "there was a ship in the offing"

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "offing":
   aftertime, afteryears, background, by-and-by, course ahead,
   crystal ball, determinism, distant future, eventuality,
   expectation, foresight, forward look, future, future tense,
   futurism, futurity, hereafter, horizon, immediate future,
   immediate prospect, imminence, near future, outlook, posteriority,
   prediction, probability, project, prophecy, prospect,
   remote distance, the distance, the future, the morrow,
   the sweet by-and-by, time ahead, time just ahead, time to come,
   tomorrow, vanishing point