This was a criminal who betrayed the core of American democracy, lied to the people, persecuted those dedicated to free speech, ordered robberies and cover-ups, and laid the ground work for some of the best innovations of the time - like the EPA - and the worst - price controls. For one generation he will always be evil. For the next he may be more complicated. Still a crook and an enemy of the Constitution. But complicated.Well, I can't really argue against "may be," but I very much doubt it.
In the long run, no one is going to remember Nixon for China; they're certainly not going to remember him for the EPA and other laws he accepted from a liberal Congress. Nixon isn't similar to Lyndon Johnson, who really is developing and deserves a "complicated" reputation because we attribute quite a bit of responsibility to him for both the major achievements and disasters of his presidency. The Nixon-era achievements, assuming that they are seen as significant achievements down the road, won't be like that. No one thinks -- or will think -- that Nixon actually cared about the environment, or thinks of him as having primary responsibility for most of these domestic policy enactments. To the contrary: the odds are pretty good that many currently overstate Nixon's domestic policy record because they like playing up the contrast with contemporary Republicans. That distinction may not matter much to future historians. Indeed, a somewhat similar vogue for Nixon's foreign policy matched the peak of Ronald Reagan's latter-day Cold War presidency, but has now (I think) faded, so that now we're just as likely to blame Nixon for his Vietnam policies as we are to praise him for detente and China.
No, specialists in diplomacy and Cold War history will debate Nixon's contributions to those things, but for everyone else Watergate is going to overshadow all that. And rightly so.
He's going to be remembered as the crooked president who was forced to resign because otherwise he would have been impeached and convicted. Complicated? Sure; all humans are complicated, and Nixon surely at least as much as anyone. But his legacy as a politician won't be especially complicated.