A null hypothesis does not have a probability. It is either the case, or it isn't.
Edit (response to your comment below) [speech restricted at the moment]:
"If you can't dispute it, you won't."
Edit2 (response to your comment/edit below):
It's just a fact. Same as the other simple facts I have stated that remain completely undisputed.
Why would you hypothesize an experiment where you already biased yourself (I assume p = 0.01? what?) on the outcome?
If your hypothesis is that you will observe no differences, then you have implicitly assigned a prior of 1. Any experimental design will be reducible to this fundamental comparison.
The p-value of an ongoing experiment is a measurement of the reproducibility of the [measurement of the predicted observations of the] hypothesis (many hypotheses are not true though; in those cases the p-values are not valid reproducibility measurements).
Edit3:
>Your misunderstanding in a nutshell is demonstrated by "if you can't dispute it, you won't", which you seem to think means "if you won't dispute it, you can't", in clear violation of Bayes's rule.
I think that that is your misunderstanding.