You could also argue that Disney is stepping up its advertising because either
a: The tourism section of the economy is still hurting from the recession so Disney wants to make sure you don't opt for a cheaper vacation close to home by constantly reminding you it exists, ORRRR
b: As the economy slowly ticks upward, Disney anticipates more people traveling in the course of the next year and, knowing how many people plan and book vacations far earlier than they actually take them, they're "planting the seed" now.
Speaking of metaphorically "planting the seed," this is also the time of year that most people start filing their taxes. An abundance of WDW ads this time of year probably is probably strategic - as soon as you find out if you're getting a return, and how much, you're thinking "I'm going to Disney World!" And let's face it, if you live in a cold(er) part of the country, there's a greater chance you're staying home more often, on the computer or watching TV more, so WDW is stepping up an ad campaign for a time of year where more people will possible see their ads. I wouldn't be surprised if, as the temperatures warm, you'd see more print and billboard ads for Disney than now, because more people will be out and about then.