I don't think they've pencilled in Stott, per se (and he seems far more likely for late 2022 or even 2023 in any case). I think they want the option to sign one of the superior SSs next year, when Cutch and Herrera will be off the books and Segura's contract won't be a burden for much longer. Probably even more so now that Dombrowski is here.
It's also possible Semien would be the best choice but he's more certain to get a three-year deal at his age, and is not without question marks himself.
The consensus is, one of these SSs will sign, and the other three will quickly follow. But who's it going to be, and by which team? I don't imagine the Reds, for instance, are going to help Didi or any of the others set the market any more than the Phillies will.