Looking for a (preferably single) word/simple phrase to refer to "the quality of a person to know that he is probably wrong about something and is also willing to accept he is wrong about it, but just has not got a chance to do it yet"
A disposition for purposeful thinking and acting guided by criteria that are considered to be contextually appropriate and that are expected to result in positive outcomes related to the purpose.
Criticality relates to (self-) reflection skills to evaluate your own behavior and check if it is in line with values and norms. These can be personally or culturally prescribed.
It is a quality found in critical thinking:
Whether a person is willing to admit that he is wrong, even when he knows he is, relates to hypocrisy, which can be seen as an incongruence between one's (moral) beliefs and actual behavior.
I would say "humility". It's the opposite of pridefulness, conceit, hubris, etc. A person with humility is "humble", and if you're humble, you don't mind being wrong or corrected.
humility n. The quality or condition of being humble.
humble adj. Marked by meekness or modesty in behavior, attitude, or spirit; not arrogant or prideful
American Heritage® Dictionary of the English Language, Fifth Edition.