User blog comment:Kashicorn/Event Time (Harrowing, Snowdown, Lunar)/@comment-5556439-20131007172412

Riot already laid to rest any hopes of another Snow or Autumn map.

Its not on their priority list at all and they know that while players do want to see a new map over skins, its just not something they necessarily want to do. They have resources allocated elsewhere and dont plan to switch.