What is the up-to-date disposition towards narcolepsy in the U.S.A. for obtaining a pilot license?
In the FAA Guide For Medical Examiners there is only a single direct reference to narcolepsy

Under the Obstructive Sleep Apnea QA section it states 


  Does this process involve other sleep disorder conditions? (E.g.
  Period Limb Movement Disorder, narcolepsy, central sleep apnea, etc.)?
  
  No. This process is for obstructive sleep apnea only. If it is clear
  that the airman suffers from a different sleep disorder, DEFER and
  submit any supporting documentation for FAA decision.


This would indicate that if you suffer from any sleep disorder conditions your medical should be DEFERed 

Earlier in the document it states: 


  Medical conditions that chronically interfere with sleep are
  disqualifying regardless of whether a sleep aid is used or not.
  Examples may include primary sleep disorders (e.g., insomnia, sleep
  apnea) or psychological disorders (e.g., anxiety, depression). While
  sleep aids may be appropriate and effective for short term symptomatic
  relief, the primary concern should be the diagnosis, treatment, and
  resolution of the underlying condition before clearance for aviation
  duties.


Narcolepsy is a sleep disorder and would potentially fall under this definition and thus prevent your from getting clearance. 

In these cases its usually best to get the advice of an FAA AME.