As others have posted, batiks will not shrink. The process of making them basically preshrinks the fabric. The manufacturers have to submerge the fabric in very hot water to melt the wax. So batiks are essentially preshrunk. This is why they seem to have a tighter weave then most other fabrics. The only thing I would be concerned about is the possible bleed factor. But if you get some synthropol to do your first wash you can avert any possible issues there, provided you don't have one of those water saving front loader washing machines.
That said, even if it does bleed you said this was a knock around quilt for DH to use on the sofa so really no matter what, this is NOT a disaster waiting to happen. Even if the unwashed JR in the quilt bleeds.