A crucial long-term issue for the profession is that financial and scientific metrics (FSM) are playing an increasing role in allocation of resources in universities and grant agencies. (There are, of course, many local variations on this.) Now, within philosophy this trend has two consequences: 1) it favors certain 'applied' areas of ethics, and complex, empirical, interdisciplinary fields of inquiry with widespread interest within and outside the academy, (i.e., philosophy of cognitive science, moral psychology/X Phi, formal semantics/artificial intelligence, maybe philosophy of biology/religion, etc); 2) it favors those who can create intellectual trends--the key becomes to be the first to generate a scholarly literature. (See, Brit Brogaard's reflections here.)
Now, many philosophers who kind of want to model philosophy on science (a legacy of 'scientific philosophy') may even be sympathetic to this trend. (I certainly was.) But given that we are a small, splintered discipline, scientific metrics do not favor us at all. Thus, as a whole, FSM threatens the very survival of philosophy as a distinct enterprise in the academy with the exception of very (endowment) wealthy US/UK private universities (and their satellite campuses in the Middle East and Asia as well as a few public flagships that emulate them), where philosophy is a kind of status symbol and/or good preparation for elite careers in law (journalism, government, etc). This is not an idle thought--philosophy departments do get closed. Moreover, it is possible that programs in professional ethics (an important source of enrollments) need not be housed in philosophy departments.
Now, one nice feature about the PGR rankings is that, on balance, these promote a relatively broad vision for the discipline. As I remarked before, on the whole PGR rankings do not reward narrow specialization and in its ongoing evolution encourage departments to have fairly comprehensive coverage of specializations. While the PGR rankings are obviously not immune to reasoned criticism, even its harshest critics should be heartened by the fact that its values are immanent to the way professional philosophy is already practiced (for good and ill--as such it reflects of course its evaluators' preferences for some areas of (or approaches to) philosophy over others). But even so, in virtue of its existence as a robust metric, PGR can well be abused in the manner of FSM. In particular, one wonders when Deans/Provosts in the Anglo-world will start using, say, low PGR rankings as an argument to eliminate PhD programs.