It would depend on the long-term effects of whatever political settlement ended the war. I clearly remember that the North Vietnamese spent the whole war denying that they had any troops in the RVN. They insisted that the VC were a spontaneous uprising and if they won there would still be two Vietnams, that the idea that the VC was just a front that would be pushed aside after victory was just American propaganda.
So one possible peace deal would involve enough of the VC members, leaders as well as troops, realize and oppose that to make a break with the North workable. That is they would try to cut a deal with the South Vietnamese Government, which according to Denis Warner - in his history 'Not with Guns Alone' - they actually did try to do in the dying days of the war.
So if you have a deal made and the NVA driven out, there would still be a hostile North Vietnam across the DMZ, but a much superior South Vietnamese government and military. The VC was after all already a well-organized government in much of the country, though blending that in with President Thieu's structure would be a challenge.
The Republic of Vietnam would go into peace with a better road/port/airport structure - courtesy of the US Army constructing such to support the war effort - than was normal in South East Asia at the time. Combined with a continuing connection to the US, both economic and military with the US Navy based in Cam Ranh Bay it would probably build up at least as fast as anywhere else in the region.
So now a fairly strong and reasonably wealthy country. Countries in Asia that were military dictatorships at the time are democracies now, so there is a lot of hope there assuming the internal peace holds.