Hextech Loot vs Skin Releases

If I save a box before a new skin is released will it have a chance of containing said skin when I open it when the skin is released? e.g Pulsefire Caitlyn 7.10 I have 3 chests now (7.9) I save them until skin release and open them on the skin's release will those 3 have a chance of that shard?

I'm sure this has been asked and answered before but i'm lazy and key words aren't my specialty.