As mentioned in on other threads that ask about crowds and how booked up the Disney hotels are, how full the Disney resorts are really has minimal bearing on how busy the parks are.
Disney hotels have a (relatively) high occupancy rate year-round, and the Guests staying at a Disney hotel only make up a fraction of the number of Guests in the parks each day. They pretty much provide a "base line" number of Guests for the parks.
In order to know how crowded the parks will be, you'd need to know how full the OFF-property hotels are. Many, many people visit Disney World and stay at off-site hotels, timeshares and rental homes. In late January the Disney hotels could be packed, but the parks are empty because there's noone in the hotels out on Route 192 and I-drive. But at a crazy-busy time like Christmas Week, when it truly is elbow-to-elbow in the parks, you have to drive quite a way away from Disney to find a hotel with empty rooms.
Disney runs promotions like Free Dining and the current B4G3 promo to entice people to either a) plan a trip to WDW if they weren't already thinking about going, or b) if they were going to go, to make them decide to stay on-site rather than off-site.
If you're going during a time that's typically not crowded (like early February), the only place you might see that's crowded as a result of the B4G3 promotion is your hotel and its pools and restaurants.
-Rob