As long as at least one of the following three things are still open, I'll still be going to WDW in 2012:
1) Snow White's Adventures
2) Main Street Electrical Parade
3) Dumbo located symetrically behind Castle for perfect firework riding
There is no way I will miss the chance to say a proper goodbye to these things in the final days of each one, as they are all Very Important Favorites for me. And since I suspect at least one or more of them will still be around for at least a portion of 2012, it looks like I'll be there in 2012.
However, as all are expected to close/leave/be relocated in the near future, I do see myself missing some years at WDW for the first time since I began attending multiple times a year again in 2006.
Not due to any formal official "boycott", but simply to choose DISNEYLAND, the Disney resort in my country that will be offering more of the things I like - including Mickey's Toontown and SIX attractions in Fantasyland that are all personal favorites and that will likely NEVER be found at WDW (Pinocchio's Daring Journey, Alice In Wonderland, Mr. Toad's Wild Ride, Casey Junior Circus Train, Storybookland Canal Boats, and Matterhorn Bobsleds). And it's been over a DECADE since I got to experience any of these, other than via YouTube videos!
The timing of this works perfectly with the new DCA expansion, as others have said. Assuming 2013 is the first year I skip WDW in favor of Disneyland, the DCA expansion will be a full year past completion and hopefully the 2012 Carsland opening crowds won't be as bad in 2013. And I'll get to enjoy the Mermaid ride WDW is getting, plus the new Carsland, plus hopefully MSEP will go back there after it leaves WDW.
In addition to the 6 extra rides in Fantasyland (soon to be 7 when Snow White closes), I'll enjoy getting to experience the Disneyland versions of MK classics, which are usually (but not always) better at DL. Plus, I'll get to experience my beloved Toontown again, this time in an even better version than the MK's, which has yet another great dark ride missing in Florida, Roger Rabbit.
Plus, DL has other classics missing in Florida, such as the Indy ride, Sailing Ship Columbia, the Canoes, and the Submarines.
The only things I'll truly miss about MK are the Country Bear Jamboree, Mickey's Phillharmagic, and to a lesser extent Carousel Of Progress, Peoplemover, and Stitch. Everything else I love at the park can be found at DL, usually in a better version.
I will miss some of the Epcot and Studios attractions, and the entirety of Animal Kingdom, but at least a few of the classics from these parks can be found in either DL or DCA (such as Fantasmic!, Star Tours, Captain EO, Soarin', It's Tough To Be A Bug, Disney Animation, Playhouse Disney Live, and Tower of Terror)
The bottom line is the only reason I've been to WDW tons and tons of times and DL only twice is due to WDW's closer location. I'll be "neglecting" WDW for a few years to give DL this much needed attention, but then again I've neglected DL for FAR too long already. I am LONG overdue for another DL trip.
I probably would have skipped a year at WDW to focus on DL anyway, with all the improvements coming to DCA - but I can't lie, the loss of Toontown and impending doom of the Snow White dark ride makes it feel more URGENT to go there; and instead of going once, I'll probably go for a few years before going back to WDW again. But eventually I'll miss the Country Bears, Philharmagic, Figment, and Animal Kingdom so much that I'll have to shift the balance and give WDW some love again.
But I can definitely foresee a future where I visit the 2 US Disney resorts more equally, even though it will be less convenient, rather than WDW having such dominance due to it's location.