the spacecraft was projected to enter the Martian atmosphere and either burn up or crash into the planet's surface.
*Mars Global Surveyor is predicted to orbit until 2046 (50 years after insertion).

Besides decaying to Mars, a collision with a moon or other spacecraft is also a possibility. In March 2017, MAVEN had to change its orbit to avoid colliding with Phobos, and with an increasing number of spacecraft at Mars this risk increases. The Mars Global Surveyor