The main benefit of having a mechanical shutter is that it hugely reduces and simplifies the circuitry on a device. Having an electronic shutter (where the sensor basically starts gathering light for a set period of time) means added electronics at each pixel location.
Yes it's true, before the release of the latest Nokia flagship the Lumia 925 there is already its successor in the pipeline, but because there is no official name for it at the moment we'll just refer to it as the Nokia EOS.