If no other forces ever act on the spacecraft, it will continue moving at 32,500 mi/h in the same direction, because forces are not required for an object to continue its motion.
The spacecraft will eventually curve away from a straight line, and its speed will change, as it comes within the gravitational influence of one or more of the objects out there in the Kuiper Belt and the Oort Cloud.
If no other forces act on the object, according to Newton’s first law, the spacecraft will continue moving at a constant velocity, assuming that a planet or something with large mass doesn’t cross its path. Forces are not required to continue the motion of an object on a frictionless plane at a constant rate.
