For what it's worth my 2016 70D just crossed 10,000 miles and has had zero issues and not needed a single visit to a SC. Of course I realize it's 5 years after the Model S began being built.
So, one silver lining for Tesla in general may be this: the quality level of the newer cars seems to be light years better than the earlier cars, according to Musk's claims and web polls here on TMC. If this is the case then hopefully the service backlog is largely due to ongoing quality problems with earlier year cars and the still-teething first year Model X's.
If most 2016 Model S's are like mine - as in, zero problems - perhaps this is an indication that Tesla plans/hopes to fix the service center backlog issue simply by building better cars.
In theory this should be possible, given that there are so many fewer things to go wrong in an EV vs an equivalent gas car - even one as complicated as a Tesla.
Of course this won't fix the problems currently of owners waiting for service - I'm only holding out a ray of hope that as service centers get built out AND quality improves, these two forces should combine over time to get wait times down.
One would think that in the long run Tesla can get by with far, far fewer facilities devoted to service than ICE manufacturers need.