Robert McNamara, the secretary of defense for JFK, said there was no plan to just pull out of Vietnam at the time of the assassination.
Dean Rusk, the secretary of state for JFK, said there was no plan to just pull out of Vietnam at that time.
RFK said there was no plan to just pull out at the time of the assassination.
The Pentagon Papers, which includes the then top secret cables and communications between the JFK White House, the Pentagon and the State Department, shows there was no plan to simply leave.
The plan was, again, to draw the troops down as the South was able, through US assistance, to take on the war by itself. The first was contingent on the second.
This is not me saying there was no plan to just leave. This is the above sources saying it.