On the face of it, when an aircraft descends 2500' due turbulance then even old 2000' level spacing won't help. Twas probably associated with a massive loss of airspeed which is caused by a large change in direction or strength in the wind - Did his ground speed change after the incident? My prediction is that it would increase...
When these sort of wind changes occur, they TEND (ie not always) to be a once off change (well the large change anyhow). Thus the RVSM status could probably be maintained. Probably a good idea (sure you did anyhow) to advise following aircraft that theirs may not....
Watched the 737 autopilot do very well in turb. Its the change in wind that causes us to get our knickers in a twist. And I have seen quite a few in the last week.
ATB, Cough