Why not? Did the non-RT 430 not exist alongside the non-RT 580? One had more power and sold for more. It didn't hurt the 580.
It's about what you can sell. Till the 600, Canon historically had high and mid level flashes co-existing, as did Nikon. Since they brought out the 600, people have been expecting a smaller RT-enabled unit to come out any day (for more than two years now).
At this point, people have sort of accepted that they have to get the 600 if they want RT- and it is such a desirable feature people are ponying up the cash. So providing a mid level RT-enabled unit now makes less sense to me.
At the end of the day, I keep emphasizing on "to me" because I don't have all the market research data Canon does. So we will find out, I guess.