CUPS already has support for being a print spooler. It already allows you to "enumerate printers, submit jobs to them, etc." What is printerd going to provide that CUPS does not?
Please keep in mind that another layer of software is another layer of bugs that we will all have to debug. Even the best programmers sometimes make mistakes. If there's no value add from the additional abstraction, then I would prefer to keep things simple.
I would love to see something take over from cups, but only if it provides the same features that cups provides. I'm not really interested in running the printer daemon version of "duelling banjos."