Oh, man, this is a toughie for me - for the last two years, I've made my yearly trips in October so I could attend Tag-o-mania, the Tagrel.com yearly gathering. Just a few weeks ago, I made my decision that next year, I would make my trip in early December, so I could attend Pixelmania, and maybe some Passporter events (should they be scheduled), and so I could try my 50D and my new tripod out on the Osborne Lights. I'm also hoping that the Lights of Winter come back in some new form next year. I miss the WDW holiday decorations. And I miss all you pixel-maniacs; it's been two years since I last saw most of you at MouseFest 2008.
If Pixelmania changes to October, I'd enjoy being able to maybe attend both Pixelmania events and possibly Tag-o-Mania events, too, but I'd really miss the holiday stuff.
I'm up in the air on this one; I'll most likely be there whichever month it's held in, unless by some miracle MouseFest makes a return in 2011. I just miss the Osborne Lights, both as something to look at and as something to photograph.