This is the moment to begin making contingency plans for Executive Office vacancies.
Either a VP or Presidential resignation or impeachment would throw the US into chaos. That's why Congressional leaders should make a concerted effort to identify multiple credible, competent replacement candidates in the increasingly likely event the 25th Amendment becomes necessary soon.
The President is very likely to have the shadow of impeachment growing closer. That means there are two other big things coming into play.
1- Trump might decide at any given moment to resign. His unstable personality combined with his persecution complex makes that possibility a real concern. He certainly wouldn't go through an impeachment trial. As in his business life, he'd attempt to find a way to 'settle' without admitting wrongdoing. That means resigning.
2- It's already apparent that the scandals enveloping Trump that might actually lead to impeachment are likely to pull Pence into the same orbit. It's not unlikely that Pence might be offered up as the sacrificial lamb if Trump believes having Pence take responsibility would provide Trump sufficient cover.
This why I think it's imperative to find a viable, willing replacement VP. I'd suggest it be someone like Lindsay Graham, Bob Gates, Chuck Hagel or even Mitt Romney who a) could win near universal congressional support b) would pledge not to run for re-election and c) is not tied to Trump or Pence. That's the type of person who could help pull the country out of the Trump/Pence morass AND be politically acceptable on both sides of the aisle.
This feels like a scary situation to even contemplate. Not having a game plan is scarier still.