There are many photoshop features not available yet in iPad Photoshop. So it may be a matted of Mockup design if a mockup template will be usable in iPad Photoshop. Does the mockup depend on a Photoshop feature that is not available yet in iPad Photoshop. There is no standard mockup design. I would bet Some mockup templates will be usable with iPad Photoshop and others will not be.