Looks like there will be 5 more PROJECT: ____ skins (6th being PROJECT: Yasuo).
Here is a link to the promo page.
There are hints (each labeled 'memory trace') for the champs who are getting them:
1. "Trace Lost" - Amumu maybe, since he has no memory?
2. "Brilliance in pieces, shrouded in ethereal flame. Protector, light bringer. Lone voice. Stand and Fight. In death heavy fields, now still she stands, light washes over..." - Obviously Leona
3. "Piercing flame, he, cast in light. I see his vision, free from shadow, a blazing melody. Beyond the light, nothing, purity bound in fury..." - Brand?
4. "Tempest, a blossom caught in drift, fluid form. He speaks. Death is like the wind... he is a storm, blade howling... Always by my side..." - Yasuo
5. "Dark sight, shadows marked, death lives beside. Silencer, he follows. The shadow is within. Blood soaked, he stands. Vanish..." - Obviously Zed
6. "Weaves, unweaves; unraveled defense, dashing forward blade gleaming. Caught orbiting one vision, dashing, striking, blade dancing..." - Probably Fiora, but I guess it could be Irelia?