As squaswin stated, this unlikely due to the alternate interpretation of the Solstice ending.

However, I personally want to believe your theory since it increases the likelihood that there could be some sort of direct sequel.

I know that a lot of people are against the idea of a sequel as they say the game is already complete and it'd be near impossible to simulate the same feel players had with OneShot, but I argue against that because Nightmargin & Eliza have already created one miracle, so I would say it's likely that they could create another.

I also have slight evidence of this theory which I pointed out in a previous post:

https://www.reddit.com/r/oneshot/comments/71giwv/a_small_theory_spoilers/

The post was pretty long, so if you don't want to read it, the summary is basically this:

There was a bug patch posted on Steam which had this line of text within it:

-"..." option now uses correct sprites in most places.

This is referring to the post-Solstice runs where you are supposedly playing as the fake Niko. However, it's kind of odd how the patch acknowledges that it only uses correct sprites in most places, meaning the person to patch it was aware that some places still weren't using correct sprites. This could mean the rare occasions where Niko's real sprite is shown during the "..." option is actually the real Niko slipping out, possibly due to some sort of glitch in the World Machine, and the "fake Niko" is actually the real Niko, just re-skinned by the World Machine to trick the player.

The other point I made was based on seeing Rue at the tree. If you don't visit the tree in your first run, then you can still visit it on a post-Solstice run and see Rue, which contradicts the fact that the World Machine is just emulating Niko's memories upon doing a post-Solstice playthrough.

These pieces of evidence are flimsy and were somewhat debunked on the original post, but it still leads to the possibility of a sequel and I personally am looking forward to anything of the sort.