Not all 550 points are even counting towards his ranking because Tokyo (110 of the points) isn't even one of his 5 highest optionals. Indoor hard tends to be Ivo's best season anyway so I'm sure he'll pick up a lot of points during October again this year. Sure it's possible he may slip back a bit, but I really wouldn't be surprised if he actually has better results towards the end of this year and climbs a bit higher in the rankings still. Aren't there two late season Masters Series which Ivo could pick up a lot of points from and he isn't defending any?
You're right about Tokyo, but only through this week. Because of the scheduling changes due to the Olympics, 2007 Cincinnati results come off next week at which point Tokyo will again be a top five optional for Ivo. As far as the late-season AMS events, he'll be defending another 110 points (75 in Madrid and 35 in Paris). Other that that, he'll also be defending 110 from Basel and 225 from Stockholm.
I agree with you that indoor hard is Ivo's best surface so hopefully he'll pick up a lot of points again and remain in the top 15. It's just not guaranteed.
On the positive side, Ivo will be moving up to #13 next week, which is very impressive (again, that's because his 110 points from Tokyo replaces his 5 points from Cincinnati last year). Honestly, I never thought Ivo would go up that high so I'm very happy. Regardless of what happens later this year, let's enjoy Ivo's accomplishments for now.