They've already expanded the strategy to three shipyards. Who says they couldn't add a fourth one for CDC?
If you build 18 to 20 CDC over a period of 25 years, you are ready for the next iteration by the time you are through with the program, so with that expansion of the fleet, there is room for another yard in the continuous build mode.
Besides, right now, my view is that the first priority for the RCN is to get the replacement and increased number of ORCA type vessels Topshee mentioned because if you are going to need to crew more ships, the rate at which we now produce watch-keepers is way too slow.