It makes sense. I wouldn't be surprised that they start having Windsor Christmases in the future. The Yorks, Wessexes, Eugenie already have homes nearby and the castle would accommodate those who are driving in better than Sandringham. Never understood why they always did Norfolk.
I can't exactly remember why they switched to Sandringham in 1988, but I think 1988 was the year renovations where carried out at Windsor, the renovations which caused the big fire in 1992.
I guess that after a few years spend at Sandringham they simply liked that "new" tradition more. It happend a lot in the family during that time, maybe they prefered to stick with NEW for the kids or so.