The Collaborative International Dictionary of English v.0.48:

Impendence \Im*pend"ence\, Impendency \Im*pend"en*cy\, n.
   The state of impending; the state of being imminent and
   liable to happen soon; also, that which impends. "Impendence
   of volcanic cloud." --Ruskin.

   Syn: imminence, imminency, impendence, forthcomingness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

impendency
    n 1: the state of being imminent and liable to happen soon [syn:
         imminence, imminency, imminentness, impendence,
         impendency, forthcomingness]