Andy Clark (philosophy of mind and cognitive science), who currently holds the Chair of Logic & Metaphysics at the University of Edinburgh (where he has taught for the last fourteen years), will become Professor of Philosophy and Informatics at the University of Sussex, with an affiliation with the Sackler Centre for Consciousness Science, effective January 2019.  That's a big catch for Sussex, which will likely propel the PhD program into the UK top 15.  Edinburgh will likely drop out of the UK top five, but will probably remain in the UK top ten.

ADDENDUM:   Nick Treanor, Head of Philosophy at Edinburgh, writes:

We’re disappointed to see Andy move, of course, but he is a great friend of the department and we’re happy for him and for Sussex.

It may interest some of your readers to know that Edinburgh expects to appoint 12 permanent faculty over the next three years, three or four at chair (full professor) level, the others open rank between lecturer/senior lecturer/reader (roughly assistant/associate/advanced associate professor). This will be across a range of areas. We are also hiring a head of school this year, a senior professorial level appointment. Tenured and tenure-track faculty are welcome to contact me in confidence if they would be interested in knowing more. 

That many appointments, especially if (as one would expect) they are consistent with the department's current quality, may sustain Edinburgh's very high ranking in the UK.