I know that many of you will disagree but Federer cannot stay dominant forever. He will remain #1 by a wide margin for a while yet I think but I really won't mind if losses like the one this week become a little more common.
I totally agree that he'll lose more in the future.
However, current No2 has more points than many No1s in the history of the game. It means he can't afford too many early round losses
in the mandatory events. Assume the worst case scenario : TFA wins IW, 3 Masters on clay and FO. He will have 600 ponts in the race and 3000 points in the entry ranking. He usually gets at least to the quarters in GS tournaments, that will give him another 750 ranking points. He'll get appr 700-1000 points from optional events. It's 4400- 4700 points in total without Shanghai, Montreal, Cincy, Miami, Madrid, Paris. So, to stay No1 at the end of the year Federer has to get appr 6000 points.
The bad thing about IW is not the loss itself, but the fact that he allowed it to happen in the 1st round.