Ultimately South Vietnam fell.
2 years after
all combat troops were withdrawn by Jan, '73.......
commies "took" Saigon in Apr, '75.
Hanoi bided its time while its allies in Washington (Uncle Walt, a lawyer soon to be Senator of New York, and lefty politicians) worked on bringing down Nixon. Hanoi knew that if the NV regulars marched on Hanoi when Nixon was still in office, Nixon would have considered such an act as negating the treaties, and the skies over Hanoi and Haiphong would have been darkened by the B-52's.