I can't see that ConsoleKit will magically stop working on systems not using systemd if systemd has features that make it redundant. Ubuntu for example has a lot invested in Upstart and probably won't be switching any time soon. Those features will continue to be developed as long as it still makes sense to do so.
No one is forcing distros to switch to systemd though, it is being adopted widely and quickly on its merits. It seems to be replacing not only sysvinit but tens of thousands of lines of shell scripting as well as tools like daemontools/runit, monit, maybe even ucspi-tcp and now ConsoleKit with a smaller, simpler and more robust system which seems like a very good thing.