This depends on how you are going to cook it. If you are going to cook it casserole style in the oven, yes, it works just fine to assemble everything the day before. If you plan on stuffing a bird with it, you want to prepare it just before the turkey (or other poultry) goes in the oven. This helps to ensure that your stuffing will come to temp at the same time as the poultry. With that said, if you are planning on stuffing your bird, you can still have the cornbread cubes prepped. You can also cook the sausage and the celery and onion mixture ahead of time. Just wait to assemble the stuffing until just before stuffing the bird.