I don't understand what the "guessing game" is exactly.Trump said he won't sign a pledge to support whoever is the GOP presidential nominee earlier this week (essentially reiterating what he said months ago). The pledge is a requirement to participate in the debates. By refusing to sign, he is ineligible. He can't decide whether he will participate, under the debate rules he isn't allowed to be on that stage.
The only reason there is any "guessing game" is if the pledge requirement is bullshit, or at least doesn't apply to Trump. If he decides to debate and is allowed on the stage, that's just another example of the GOP deciding that rules do not apply to Trump. So that is probably exactly what will happen.
