I think its possible, but probly not in the way we understand it, individually, ants are not 'intelligent', but as a collective they are, just like our brains, individual cells have no real power, but combine millions together, and here we are
Theres another issue aswell tho, although the common belief is that bigger brains = more intelligence, thats not entirly true, after a certain size increase the brain functions slow down, probly due to the extra distance that messages have to travel, so if an ant colony reached, for eg 2 million ants, possibly enough to initiate a consciousness, it may be that they never do, as the relative size compared to a human brain would be huge, hence the messages would be allot slower between the cells/ants
theoretically that is