Well, what you're describing is a hypothesis, not a theory. But anyway.
The box itself is almost entirely likely to be the final design. It replaced the original placeholder box art this month, and the game is going gold in October or early November if they plan on shipping these things in time. The fact that they very clearly followed a distinct and purposeful pattern, while deviating in only one spot to make room for a character that has to be an echo within a small span of characters, is what gives "box theory" a leg up on other "theories" or leaks.
This does not at all mean that it's proven, or that there isn't a slim chance of the box art being changed, no matter how unlikely, or that there aren't other characters after #69 inexplicably placed on the back or bottom of the box just because. Box theory is not proven true, but let's not pretend any other theory or leak is, at this point, anywhere near as credible as it is.
Also, to everyone in the thread, let's remember that A) this is the leak thread, not the speculation thread, and B) that the game will be out in two months and change. Relax. We'll all know soon and then none of this **** will matter.