Maybe it's different in different markets, but in my area, every movie released in 3D is also released in 2D.
They're usually released simultaneously for blockbusters, e.g., 1-2 IMAX screens showing 3D and 1-2 screens showing 2D. For others, they might start out only showing 3D on opening weekend and then transition to 2D as the movies age and move to smaller screens, e.g., Rogue One is still playing in my area but only available in 2D now.
They're usually released simultaneously for blockbusters, e.g., 1-2 IMAX screens showing 3D and 1-2 screens showing 2D. For others, they might start out only showing 3D on opening weekend and then transition to 2D as the movies age and move to smaller screens, e.g., Rogue One is still playing in my area but only available in 2D now.