Someone posted this on a Taiwanese forum. They even included where they found the information (different client files). It looks like they ditched the old champion design completely.
Sejuani's basic attacks apply Frost, reducing enemy Movement Speed by 10% for 3 seconds.
> ==============================================
> Arctic Assault (Q):
> Sejuani charges forward, dealing 60/90/130/170/210 (+0.4) magic damage and applying Frost to enemies. Sejuani stops upon colliding with an enemy champion.
> cost 70/80/90/100/110 Mana
> cooldown 19/17/15/13/11
> range 700.0
> ==============================================
> Northern Winds (W):
> Sejuani summons an arctic storm around her for 5/5/5/5/5 seconds, dealing 12/18/24/30/36 (+0.1) (+ [1/1.25/1.5/1.75/2% of maximum Health]) magic damage each second to nearby enemies.
> Damage is increased by 50/50/50/50/50% against enemies affected by Frost or Permafrost ( magic damage per second).
> cost 40/40/40/40/40 Mana
> cooldown 10/10/10/10/10
> ==============================================
> Permafrost (E):
> Sejuani converts Frost on nearby enemies to Permafrost, dealing 60/110/160/210/260 (+0.5) magic damage and increasing the Movement Speed reduction to 30/40/50/60/70% for 3/3/3/3/3 seconds.
> cost 55/55/55/55/55 Mana
> cooldown 11/11/11/11/11
> ==============================================
> Glacial Prison (R):
> Sejuani throws her weapon, stunning the first enemy champion hit for 2/2/2 seconds and all other nearby enemies for 1/1/1 second. All affected targets take 150/250/350 (+0.8) magic damage and are affected by Frost.
> cost 100/100/100 Mana
> cooldown 150/130/110
tag:tank
range:125
move speed:315
armor base:17.5 (+3.5 per level)
mana base:220 (+40 per level)
mana regen:1.29 (+0.09 per level)
hp regen:1.45 (+0.17 per level)
magic resist:30 (+1.25 per level)
hp base:450 (+85 per level)
attack:54 (+3.5 per level)