The 50D turned into the 60D, which was described as the "Super Rebel" as build quality and size decreased. The camera was a bit of a bust and the 70D corrected that by moving upmarket.
I suspect Canon is moving the Rebel back into that "Super Rebel" slot.
A part of me is wondering if the xxD line is nearing its end.
The 70D moved upmarket in terms of capabilities but not in terms of price.
I think you need to have something between a $600 Rebel (body only) and an $1,800 7D Mark II (body only). Whether they call than a Rebel or an xxD makes little difference, but if you do call it a Rebel, then something has to fill in the low-end. Maybe they think that's the SL1.