Canon can keep the current 17-40/4L as a budget lens, and still have a sharp (more expensive) 17-40/4L (or 16-35/4L) as they do with the 70-200/4L and 70-200/4L IS, I think that is exist a demand for both of them...
The reason for the non-IS tele lenses being still produced imho is that for sports IS is useless, esp. when using a monopod - so there's a "legitimate" demand here.
For other, shorter lenses I doubt if Canon would want to expand their lens zoo, they'd rater make a superior version and discontinue the old one - or they could have also kept the much less expensive 24-70/2.8 mk1 when the mk2 was out.
Meaning: I doubt they'd keep two 17-40L around, and more expensive would run into marketing problems, so I doubt they'll discontinue the current 17-40L (thread title), but they'll surely add a premium 14-24L and might even do a 16-35L mk3 with IS sometime if Nikon has it.