Yes, the game will run at a lower frame rate, IF you stay at ultra settings.
Depending on current settings you should restore the frame rate by:
Dropping one notch from ultra.
Turning AA down or off.
don't have the game myself so I obviously don't know the exact setting names they have chosen but you can also try:
Turning fog and smoke details down
Reducing the density of flying debris during explosions.
Changing them will help to reduce the transient framerate dropoff you see whenever there's a nice, big, loud explosion.