We've seen Canon recently bring out several new EF non-L primes with IS (24/28/35), and I expect we'll see an updated 50mm with IS soon. The IQ of those new lenses is quite good (compare the 35/2 IS to the Sigma 35/1.4 Art, for example).
I also think the next Canon 50 mm, be it 50 f/2 IS or 50 f/1.4 Mk II will have quite improved optics competitive with the new offerings from other companies. I realize "real" photographers enjoy the size and weight punishment dished out by the likes of Sigma 50 ART and Otus, but I for one love the lighter and smaller primes Canon has been putting out.
The real problem is WHEN is Canon going to bless us with their new 50 mm