Caitlyn is coming up on 4 years soon whereas Jinx hasn't even hit a full year yet (she was released Oct 10th of last year). Yes I want a new Jinx skin but no I don't believe it's not fair that she only has one while Cait has a million. Riot has done a really good job these past months giving us a mix of skins for champions with a lot of skins and champions with only their release skins. We got a new Aatrox, Nami, Syndra, Lissandra, Yasuo, and soon to be Kha'Zix skin this summer, all of which only had 1 skin. So what if Heimerdinger, Malphite, Vi (who only had 2 skins), Ez, and Cait got another new skin in the process? It's just as bad to brush off making skins for old champions as it is to brush off making skins for ones without any.
Jinx will get herself a new skin soon, but it's totally fair that the chick who has been around for 4 years got a new skin. Cait hasn't gotten a new skin since 2011, the year she was released. She got Resistance and Sheriff on release, she got Safari that May, she got Officer in October, and then she got Arctic Warfare in December. Aka it's been almost 3 years since her last skin.