I'm calling it now. The boss will be a massive shank. The Father of Shanks will be 500 feet tall and contain within him a shank production factory, constantly churning out wave after wave of the shielded blighters. During the fight you have to enter his body through an exhaust vent and shut down the factory. Only then is he vulnerable to attack while he undertakes internal repairs. Gjallahorns at the ready! Hmm what else could the boss be?