This looks suspicious to me.
Say Canon makes a new 24mm prime. Why make it f/2.8 (rather than f/2) & why add IS?
If Canon makes a 24mm f/2 USM with good IQ, I'll buy it immediately. If it's f/2.8, it's not fast enough relative to the 24-105mm f/4 for me to really consider it, and I'd wait for the Samyang 24mm f/1.4 to be reviewed.