Yes. Simple style templates (.isty) and template bundles (.tb) created in PA 5 can be used in PA 6. In the case of template bundles be sure that you use the same or later version of Adobe InDesign that the bundle was created with. In PA 5 these files are stored in your My Paratext Projects folder. You will need to copy them to _PA_StylesAndTemplates in your My Paratext 8 Projects folder in order to use them in PA 6.