We need someone in authority to step up, tell the American people what is going on, and take the heat for it.
So Wyden spills the beans, goes to jail, and then we're left with no one on the inside that will let us know that the intelligence community is still overstepping their bounds. As a bonus, after Wyden tells everyone what's going on, the executive branch refuses to take any action and continues to cow the legislature into letting them do what they want because the rest of the Intelligence Committee is largely a stunning exercise in uselessness.
As long as he remains in office and on the Committee, Wyden is doing more good being on the inside - certainly more good than those like Dianne Feinstein, Barbara Mikulski, or my own state's elected dickhead Marco Rubio. Only in the event Wyden loses his place on the Committee or fails to get re-elected would coming out and telling everything he knows be potentially useful.