Skullgirls is a 2D fighting game developed by Reverge Labs and published by Autumn Games. The game was released through the PlayStation Network and Xbox Live Arcade in North America, Europe, and Australia from April to May 2012, and later received a Japanese release by CyberFront for the PlayStation Network in February 2013. A Microsoft Windows version, developed by Lab Zero Games and co-published by Autumn Games and Marvelous, was released in August 2013. A Japanese arcade version, produced by M2 for the NESiCAxLive service, was released in 2015. A mobile spin-off of the game, developed by Hidden Variable Studios and published by Line, was released for Android and iOS devices in May 2017.
The webtoons deal is still alive and well according to Cellsai, it's just "taking longer than expected to actually produce" (SG Discord). Besides, the Twitter post about it announced its "early pre-production", so there wasn't ever really an indication of its release being anytime soon other than the dubious "coming soon" caption, and if guilds are any indication, that doesn't mean anything. The two artists mentioned were also involved in animating Annie from what I understand, so that might have also contributed to its late release.