The first 4 packs had unique skins but had old perks. After that, we have had homebase characters be in packs (which in my opinion is lame as fuck since the packs are $16 each). But I realized that there aren't many characters left that they can make packs with. The only characters left to my knowledge are Pop, Kevin, Dr. Vinderman, and Desiree. I highly doubt Pop or Kevin will get skins since they aren't as remembered well as Ray and Lok, while Desiree needs a completely new model since she has never had a 3d model to my knowledge and I highly doubt Epic has the "money" to make her a hero/skin. Same goes for Dr. Vinderman. Plus both are "dead" (we technically don't know since Epic can't add a basic Twine Story line to end the story).
At this rate, I think soon or later we will be getting the old stw packs back, starting with Metal Team Leader, and then it will be an endless cycle of old packs returning.