There will not be any more skins. Nova Covert Ops did well enough but they found that it was a lot of work for something players would only do once or twice. So they focused on Co-op Commanders, War Chests, and the occasional announcer while making the game free-to-play.
The new business model was very successful. However, there was a lot of shareholder pressure to move focus to getting some new releases out other that expansions and remasters. Everything got reorganized and the titles under Classic Games lost a lot of budget and personnel.
The guys remaining on the SC2 team like Tim Morten, Kevin Dong, and Ryan Schutter really wanted to make a new Warcraft or Starcraft RTS game but it became clear that Blizzard wouldn’t approve it. So they helped get the ESL Pro Tour started and got Patch 5.0 out with the help of developers from other groups. Then they left to found Frost Giant and start working on an RTS game called Stormgate.
Almost immediately afterwards, Blizzard announced that there would be no further paid content for Starcraft II or Starcraft Remastered. Rather than replace the team leads they cut Classic Games down to a basic maintenance staff. ESL, TeamLiquid, and Shopify started handling new map pools. A community group was formed to advice Blizzard on new balance patches. And the IEM Katowice championship portraits Nicolas Chaussois does for ESL get made into yearly free portraits. More recently, Heroes of the Storm joined the Starcraft games in the “No more paid content” status while Warcraft III Reforged got moved under the Warcraft team so they could finally add some of the features that were supposed to be included at release.
So, the only cosmetics we’re likely to receive going forward are the occasional portraits.