That actually seems pretty likely to me, considering how the official description of the fim says that the monsters "threaten our very existence"- perhaps they might breed out of control and overrun civilization, hunting mankind to near extinction, if they aren't stopped, similar to the baby Zillas in GINO. I'm guessing that they'll be very similar to the Gyaos in the Gamera trilogy, in that they will be living hidden underground until they are disturbed/awakened by pollution, nuclear testing, or some other environmental problem caused by mankind, and will start eating people and breeding, with the only hope of stopping them being the military and a much more powerful monster (Godzilla) working together, intentionally or not, to destroy them. Maybe the sinkholes that the viral marketing seems to center around are either caused by the environmental problem and release the MUTO monsters into the world or are actully created by the monsters themselves burrowing up.
