I think it's getting too hard to predict now. I know everyone wants to find that magic time frame in which there won't be massive crowds, but those windows of opportunity are getting more narrow and elusive as time wears on.
First of all, we don't know when the holiday season will start in 2011. This year and last year it had an earlier start date (two weeks before Thanksgiving), but looking at the calendar for 2011, I have a hunch that the season may begin a bit later in November, closer to Thanksgiving. I could be wrong on that, but I have a feeling that HalloweenTime will begin and end a bit later than usual, so that would automatically affect when the holiday season begins. The closer it is to Thanksgiving, the more folks will be off of work and school.
Some people have said that as soon as Thanksgiving weekend ends (not the holiday itself, but the whole holiday weekend), things lighten up a bit for a week or two. Around mid-December it begins to get really busy. I purposely chose mostly weekdays for my trip this year in December (I was there 12/12 - 12/15), hoping it would be less crowded, and I went earlier in the month than I normally go, and it was still very, very busy. I was surprised. And when I was there in November, it looked like it may as well have been the weekend right before Christmas, it was so crowded.
Some CM's have said that this whole holiday season has been super-busy and there have been no slow periods at all. Last year was the busiest holiday season (as a whole - not just December) in 10 years, so it doesn't shock me if this year equals or surpasses that.
Next year there is also the possibility of the Candlelight Processional moving out of
Disneyland and into DCA. The CP usually brings big crowds in early December to DL itself. I'm not sure what will happen if it moves to DCA or if it will happen yet, but it has been talked about. There has also been talk about a Very Merry Christmas party (like the Halloween party) coming to Disneyland...possibly in 2011. If that happens, things like the parade and the snow on Main Street may become exclusive to the party - a separate ticketed event - and only shown on certain nights.
I think there will be many changes coming to DLR for the holiday season - it's just a matter of if they will begin to happen in 2011, or possibly hold off until 2012, when all of the work in DCA is finished. In any case, these changes will certainly increase crowds levels in boths parks and perhaps shift around the times in which it is busier or less busy (if there is even such a thing as "less busy" now!!). Stay tuned to the Christmas superthread for info and breaking news!