If I recall correctly, it was in 2004 when wild pigs were first reported to be in Colorado. In 2010 there was an estimate population of wild pigs to be between 200 and 700 animals; pretty piss poor population growth. But then there have been eradication projects on public lands that have taken place. But still,over this amount of time, it's easy to state with confidence that pigs are not all likely to take hold in any real numbers, not in Colorado anyway. But if you want a very informative read on wild pigs I suggest:
Wild Pigs
BIOLOGY, DAMAGE, CONTROL
TECHNIQUES AND MANAGEMENT
Savannah River National Laboratory
Aiken, South Carolina