Being the huge DLR at Christmastime nut that I am (even though I was only able to get there for one day this past December, it was better than nothing, and I was not going to miss out on the fun!), I can't possibly tell you to NOT go in December!! I can see the lure of the
D23 event, though. The
only reason why I think December of 2012 would be a better option than December of this year is because all the DCA changes should be in place by then - the Little Mermaid ride, Carsland, the Toy Story musical, the new entrance to DCA, of course, World of Color, maybe some new restaurants and shops by that time, etc. And, most likely, a bigger deal will be made of DCA at Christmastime in 2012 than in 2010 or previous years, simply because of all the new stuff that will be there. Also, there will be many more PhotoPass opportunities by then because of all the new DCA things. Those are the ONLY reasons why I would say go in 12/12. Otherwise, I would say that the prices for everything in both parks - tickets, hotels, food, merchandise, all of it - will likely be a lot higher in 12/12 than they are now!
But, as you say, if you choose to go for the D23 event, that is basically right around the corner, so you would have to get that trip together rather quickly.