We are starting the countdown tomorrow, mostly because traveling-companion-Grandma strongly suggests/basically requests it. We'll see.
I've been talking about it for months, because I know him. When I first told him, it was "NOOOO! I don't want to go to DISNEY WOWOLD!" (Terror) Then "We CAN'T go there, Mommy! Disney Wowold is NOT REAL!" (skepticism) Then "when are we going to the DISNEY splash pool, Mommy?" (legitimately only interested in the hotel pool) And finally "Let's go to Disney today!" (in "this is a good idea!" mode.) He's nowhere near as excited as I am, though, which I am very good with (it was over-hyped for my first trip, which was miserable. Mostly because my brother expected perfection.) It was 7DMT and Barnstormer videos that made him start to think it MIGHT be OK, and the steam train that fully convinced him that he wants to go. He tends to resist new ideas, unless he's been exposed to them. I've shown him videos of the park, the resort, character meetings, rides he might enjoy. It might not improve WDW itself, but it will improve the drive.