We'll be based in Colmar for three days in early December. Would you rent a car to see the Route du Vin that time of year?
The towns on the Route du Vin will still be there. No flower boxes in the windows. There may be snow on the ground or high in the Vosges. If you do not wish to rent a car, you can get to many of these towns quickly on the public buses or trains from Colmar.
frankly one cute Alsatian town is much like another and in December you don't have the storks, the beauty of the vineyards etc etc. and it is likely to be gray and rainy. I'd have more fun spending time in a town or two rather than doing the circuit at that time of year.
Have you looked into whether any of the small towns have Christmas markets, special events,, etc? That might make it worth it. Recently, I went on google maps to show someone how cute the town of Eguisheim looks. Back in 2012 when we stayed there, the pictures on google maps were done during the time flowers were blooming in window boxes. This time when I went to "street view", it looked like it was Christmas time. Still looked wonderful to me, and made me want to go at Christmas time.
I'm actually planning on visiting the area next December (2015) for the Christmas Markets. Here's a website you might want to take a look at: