that (all) depends
The possibility or likelihood of some outcome depends on one or more unspecified factors. A: "So, would you be willing to join our company?" B: "Well, that depends—what kind of salary are we talking about?" Is it legal? Yes. Is it ethical? Well, that all depends.
That (all) depends.
My answer depends on factors that have yet to be discussed. Tom: Will you be able to come to the meeting on Thursday night? Mary: That all depends. Bob: Can I see you again? Sally: That depends.
it/that (all) deˈpends
(informal) perhaps; possibly: ‘Would you marry him if he asked you to?’ ‘I might. It all depends.’‘But is it right to send people to prison?’ ‘It depends what you mean by right!’