Where I live a 70D body costs about $1250. On initial release a Rebel Txi usually costs around $1100 with its crappy kit lens (they cost a lot less at the moment, but that is because the T5i is relatively old now). If what you say is correct, and they released a T6i with marginal improvements over the T5i, then it is going to have a tough time competing with the 70D. Who in their right mind would buy a T6i when for a little bit more they could get a much better camera in the 70D? I think one of the problems with Canon's DSLR lineup is that they have too many models on the market. It is not really economical to support future development of all of them.
It is much simpler for Canon to reduce the price of the 70D one or two hundred dollars than it is to start producing a new camera.