"From beginning to end it [Rolling Thunder] was a pure air campign--though the possibility of supplementing it by a ground invasion was often discussed in Washington, D.C., nothing ever came of the idea. Had it been realized, then almost certainly the outcome would have been an even larger and less controllable insurgency." Martin Van Creveld, *The Age of Airpower*, p. 187
https://books.google.com/books?id=SUdAJE8FRi8C&pg=PA387
These are the common assumptions. I think post war Vietnamese sources support all that. Their defense plans circa 1965 - 1975 cover this, as do their post war recollections. However...
Are they out to conquer all of North Vietnam, or get them to stop support of the VC and smash them up a bit to make them less of a threat? The former would just result in a more hellish war, one that would be won with mountains of corpses or one side giving up, the latter would make things easier to win the war long-term, as a big contributer to the insurgency would be out of the picture and the US could focus more on COIN.
There are some bits from that era, untouched by post war handling which suggest the N Vietnamese government was very worried about a US invasion though 1966 or 1967. Further these atedilluvian bits indicate the actual strategy of N VN would have been to swiftly negotiate a cease fire, and a peace if necessary. Their rational in those years was their army was in no way ready to resist what they thought would be a invading army. Air defense lacked sophistication, depth, and staying power. The regular army was not fully mobilized, trained or armed as it existed a few years later. Support by China & the distant USSR was still uncertain.
If getting the US Army to pack up and leave required throwing the VC under bus & signing a unfavorable treaty thats what Ho & Co. would do.
For one take on this I'd suggest Frances Fitzgeralds 'Fire in the Lake'. Published in 1972 it reflects research conducted back when every major offensive the NVA had attempted had militarily failed & when the historical narrative of the leaders was not yet one of a invincible Vietnamese communist peoples army. Fitzgerald goes so far as to mention a few sources for this alternative take on the N VN attitude towards a US invasion circa 1964-66. I'll leave it to the reader to judge the usefulness or accuracy of those.