Doubt we'll see Shinryu for 2.0 storyline. Maybe 3.0 but for now we seem busy with Ascians/Zodiark and Ishgards little secret vs. dravanians and Midgardsormr.
On another note it's important to remember that Midgardsormr is not a primal, Bahamut is however. So the two being related doesn't seem plausible (other than they are both dragons that is).