I studied textiles and dying fabrics in college. We did a lot of experiments with natural fibres and many different dyes. The only time hot water is used is during the dying process itself. It is not necessary to pre-wash batik fabrics. If you wash the batiks in hot water they will continue to release color. Wash batiks in cold water only, just like any other dark or bright fabric. It is normal for small amounts of color to continue to release. Ironing your fabric will help to set the colors after it has dried (air dryed only). If you make your quilt with similar colors in your palette and grey as a neutral you will have a gorgeous quilt for the long term. I love working with batiks and have many beautiful quilts that have been washed without a problem.
There are a few natural methods to help retain dyes. Here is a good link to some helpful tips.
http://www.craftsy.com/blog/2014/03/...c-from-fading/