I'm not sure if anyone has written about this yet, or even thought about it, but beyond the discussions the incident provoked about race in football, Terry's guilt (or innocence), whether or not he should captain Chelsea and the English national team, et al, I would argue that a subset of interesting subplots emerged in the months that followed that were directly related to it.
By my estimation, these are all linked in one way or another to John Terry's (alleged) comment:
1) Fabio Capello resigned after refusing to drop Terry.
2) Harry Redknapp was instantly linked with the job, which destabilized Tottenham and ultimately caused them to drop to 4th, meaning that they missed out on the CL spot after Chelsea beat Bayern. If Modric and Bale leave this summer, I'd argue that their departures were yet another ripple effect from the incident.
3) Roy Hodgson became England manager. This is of minor importance, though we never would have said "Hodgson" and "England" if Capello hadn't walked out.
4) Rio was dropped from the national team, apparently reopening a national discussion on race and creating an unexpected rupture in the longstanding defensive partnership for the English national team.
5) Most importantly, Chelsea lost to QPR that day. If we had won, we would have edged in front of Manchester United to climb 3 points behind City. Instead, the loss began a bad streak where we took 24 out of the next possible 51 points. AVB was fired and RA promoted Roberto Di Matteo, which directly led to a change in form and eventually a cup double. I don't think that anyone would argue that we would have won either cup if AVB had retained his position. Maybe the club would have gone on a losing streak anyway, but the JT incident and the loss that accompanied it put everything off the rails. By expediting AVB's firing, that losing streak contributed to RDM's arrival and our miracle run.
6) By winning the Champions League (again, inconceivable if AVB had stayed), Chelsea contributed directly to Guardiola resigning and the Barcelona dynasty taking a significant blow. Our surging form (at least in Europe) meant that Bayern Munich also lost out on a chance to win the UCL on their home ground.
For a verbal incident that occurred at the end of a relatively meaningless game, this event really set off a fascinating series of events. I'd count Tottenham, the English national team, QPR, Rio Ferdinand, Anton Ferdinand, Harry Redknapp, Andre Villas Boas, Pep Guardiola, Barcelona, and Bayern Munich as victims of John Terry's (alleged) comment. Ironically, the major winners were John Terry and Chelsea, and I suppose Roy Hodgson (and maybe Bale and Modric if they get huge contracts elsewhere). Pretty interesting, I think.