The Collaborative International Dictionary of English v.0.48:

Obsolesce \Ob`so*lesce"\, v. i. [L. obsolescere. See
   Obsolescent.]
   To become obsolescent. [R.] --Fitzed. Hall.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obsolesce
    v 1: become obsolete, fall into disuse; "This word has not
         obsolesced, although it is rarely used"

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "obsolesce":
   age, antiquate, be superseded, become extinct, become obsolete,
   date, fade, fall into disuse, fossilize, fust, go out, grow old,
   lose currency, molder, obsolete, outdate, pass away, perish, rust,
   superannuate