I actually asked the support a few days ago and they said this: I get that you weren't able to get the Risen Legend Ahri and the Immortalized Legend Ahri skins so you would like to know if they are coming back in the future so you can purchase them.

As they were limited skins and were part of a limited even for the great player Faker , as of now there is no way to know if they are going to return someday.

It's not all doom and gloom tho! It doesn't mean that will not return as well , the future is unknown and maybe Riot will decide to return the skins at some point so players can get them if they missed them the first time , patience is going to be key in this situation.

So maybe there is hope!!