I don't think Nixon would live long enough to make it to trial, under these circumstances I could see the various security apparatuses and intelligence agencies deciding that having Nixon take the witness stand, with EVERYTHING that he knows would simply be too dangerous. Not just for the nation, but their own careers!
I think Nixon would be 'taken care off' by these forces before a trial could be conducted to ensure his eternal silence.
Contrary to tinfoil hats, the American government does not engage in conspiracies to assassinate presidents. There are no smoke filled rooms of the Illuminati. Only a bunch of barely competent, flawed humans. If you want evidence for why conspiracy theories don't happen, Watergate is it.