Help w/ Skins

Hey, does anyone have know if there is a September skin sale list? I'm planning on buying an Elise skin but I don't know if I want to hold off because it might be on sale this month. Also, do all of the SKT/TPA etc skins become available when the season ends? * (and Championship skins) ? I want to buy SKT Kalista or Championship Kalista also but I don't know if they're going to become available this year or next year. I think they come available once the finals are here right?