The Department for Transport has confirmed that step-free access to the platforms at Palmers Green and Alexandra Palace stations is still planned, but not for another three or four years.
Joanne McCartney, London Assembly Member for Enfield & Haringey (and as of this month, Statutory Deputy Mayor of London), this week published a letter from the DfT assuring her that "Access for All" schemes "will be proceeding", but are "in the early stages of planning". The letter stated that Network Rail "is currently aiming to to deliver the schemes in 2019/20".