What's the big secret? Everyone has already copied their design. . I'm sure they 're working on one as we speak. They're losing too much market share in the whole conceal carry frenzy. I had a PPS for awhile and with a flush mag its the perfect cc weapon. I don't care for Walthers' relationship with S&W though. I fell for the Gen4 hoopla. It's no better than a Gen3 and some might say worse. It was a gimmick and it worked. If they released a single stack version of the 9mm and .40 sells would go through the roof.
Glock already tried the single stack with the G36. It didn't sell well. That was long time ago. If they were going to continue with the slim line, they would've done it long ago. They don't need to expand the line; they've still got the market cornered. All these pocket size pistols are great, until you actually shoot them, and then you realize how unpleasant they are to shoot.
Besides, in all of these pocket guns, at most they are .19 inches thinner, with most being .18 inches thinner, and the rest of the dimensions being the same. For that slight reduction in thickness, you lose 1/3-1/2 of your magazine capacity.
I've been through several of them and I keep coming back to the baby Glocks. The PPS was junk and it was painful to shoot enough to be proficient with. The same is true of all of its direct competition. When you lose the ability to get a solid two hand grip, you give up a lot.