It is no secret in the last couple of years, the Sigma ART line of lens have given companies like Canon, Nikon and Zeiss quite a competition with photographers looking for a high quality lens without shelling out premium prices for high performing glass.
Canon has been redesigning its entire line of shorter focal length prime lens. Starting with the EF 85mm f/1.2L II and the EF 50mm f/1.4 II and EF 50mm f/1.2L II lens. The new design will include a floating element similar to the upcoming EF 85mm f/1.2L III with improved focus shift. The new lens will be lighter, faster and may come with the latest Blue Spectrum Refractive Optical technology.
Canon UK has actually listed the EF 50mm f/1.4 as a discontinued item. See their website link. If that is not a mistake, we should expect its replacement fairly soon, perhaps in Q1, 2016.