He'll never testify. It won't happen. If we've learned anything, its that yes, Trump is 10000000% above the law. They subpoena him, he says no. They double-dog dare him to come, he says no. Now what? Call in Dog the Bounty Hunter? High speed chase in a white Bronco? Trump, for all his bullshit, realized something profound. America is not a nation of laws, its a nation of traditions. Traditionally people follow subpoenas and get prosecuted for perjury. Trump called the Government's bluff, and the Government backed down.
Even if he does testify, two things happen. One he pleads the fifth endlessly, or two he goes off on a full rally rant about Jews and stolen election of the Steale report and Hunter Biden, the committee loses all face, Trump gets quadruple digit support, Republicans win big in the midterm, impeach Biden, impeach Harris, declare Trump the new president, the supreme court swears him in and he has all members of the Jan 6th committee up against a wall and shot, and declares no new elections, all to the screaming frothing at the mouth support of hundreds of millions of Americans.