You really ought to just play it by ear. You can always find a place to stay before Christmas, and that way, you can follow the good weather. The only exception is if you are going to fly. If so, I'd suggest flying into Denver then playing it by ear. But Summit county will be your best bet because of the elevation and snowmaking. Keystone usually has some good cruisers open, but expect you'll be staying on-piste.
I go up to Mt Snow for the 2nd week of December every year (9 years running), and we get some really good and really bad weather. This past December we got 6-8" one day, rain one day, and generally good conditions. The two years prior were horrible (to the Nth power). But the teo years before that were amazing, with 80-some trails open and 18" of freshies (single 18" dumps) both of those years. Actually, it was so abysmal three years ago, that 8 of us cancelled (with penalties) and flew to Crested Butte. Boy are we glad we did!
So don't make any non-refundable plans, or better yet, just plan on going SOMEwhere, but don't make lodging plans.