There is no reliable rumor of a 50mm f/1.2L II. There's plenty of speculation though... and there has been for years.
All the present rumors are now on the theme of "well, it's one of the few lenses they haven't updated yet". Well, so what? If it ain't broke, don't fix it. Canon don't OWE anyone a Mk2 and the price of the original lens is now quite low. You just know that any future release will be much more expensive.
Canon don't need to release a Mk2 in my opinion. The existing lens is a good one. It performs exactly as it should. That f/1.2 aperture is quite useful over the f/1.4 ... and the tough construction and weather resistant sealing goes a long way to sell it. Until Canon drop a hint that there's a Mk2 on the way you should pay little attention to fanboy rumors. They'll always be floating around. Besides, the only patent lodged by Canon for a 50mm lens recently turned out to be a 50mm f/1.4 STM lens... designed to kill off any interest in the Sigma alternative with an outrageously low price tag of just $349.
I really like the EF 50mm f/1.2L USM lens. I've been shooting with it for a few years now and it's one of my two favorite lenses. On a full frame camera, it's actually a decent walkabout lens. But if shooting portraits of people or pets, or when shooting products or nature... it produces a lot of very "luminous" images for me and most are keepers.

Sometimes the lens spits out some lousy photos, but that's usually a result of either poor lighting/composition and me being lazy with it haha On the other hand, put in the work with it, and it'll make some phenomenal photos! 
