Well, if Trump was impeached, then there wouldn't be any choices. The VP is going to become the president.
Trump and Pence will, or should also, both be impeached or resign along with parts of the Cabinet eventually. Watch for the momentum building and it coming for Asshole Pence with a tie in FIRST to the Flynn bullshit and cover up, and then the whole house of cards falling on the slimy ball of hypocrisy!
The time for Trump and Pence will come toward the end as the pyramid of corruption is built and the capstone is nearing its placement. That is, of course, if the investigation isn't derailed with the full intent to obstruct by either direct or indirect means!