First time since the 2004 that someone outside the Top 8 has won a Slam (French, Gaston Gaudio) and only the second time since 2003 we've had 4 different winners of each major in a year.
Can't see this as the "changing of the guard" though. Nadal is out injured, Murray is still recovering from some pretty serious surgery and Djokovic has had a bad year in general and Federer is improving on what was a terrible year last year. Admittedly players are much less intimidated playing the "big 4" now but I still think normal service will resume next year, at least with Murray and Djokovic.
It probably won't be a classic, but still a great opportunity for Nishikori to finally break through and for Cilic it is probably his one chance to win a Slam. Kinda wish Monfils had beaten Federer though now, would have loved to have seen him in the final.