I could see another attempt for the presidency in '68; it would only buttress his case with real executive experience. Perhaps Ronald Reagan might opt for a Senate seat instead of the governorship?
Seems to me that the unspoken issue is what might a successful run for the governorship butterfly away in terms of Nixon's psychological makeup: recall that "...won't have Nixon to kick around..." press conference in 1962. Now, would his paranoia not be as strong? And if not, would we butterfly away Watergate, yielding a full two term Nixon presidency? In turn, would that obviate Carter, and thus by extension, a Reagan presidency?