Creating depth map from a 2-D image? My question is oriented towards the generation of depth map using any of the state of the art depth sensor.

However, each of these method required the presence of an 3-D object in front of the sensor. Is it possible the generate a depth map even if a 2-D image is presented to the sensor?
No, it's not. The way many of the 3D sensors work is by projecting an infrared pattern onto the surface and measuring how it distorts. But with a 2D image, the pattern will simply be projected onto the flat 2D image, not onto the objects in the scene. So the 3D sensor will only sense a flat card.

Other methods work by combining 2 images taken with different cameras at different angles. This will have the same result as above. The 2D photo will be interpreted as a 2D surface by the combination of the 2 cameras.