It's certainly happened before in World Cup tournaments. Hungary had to junk a Winners issue in 1954, when it lost to West Germany in the final, as did Netherlands, when it lost to West Germany in the 1974 final. The Netherlands also had a Winners set ready for the 2014 tournament, which will also be destroyed.
In 1978 when Scotland made it into the tournament final series, the Royal Mail had a design prepared if Scotland actually won the World Cup:
http://www.footballphilately.com/20...rs-1978.html