Whilst we don't know how the 'investigation' looks at this today, we do know that we can't definitively say that ACARS was disabled (neutral term) before the last transmission.
We only know that ACARS did not make it's expected transmission at 17:37. This would place the time of disablement between 17:07 and 17:37.
There is some thought that the disabled transponder event should have triggered an ACARS message (can anyone confirm or refute this?). If this is true, then we would be further able to deduce that ACARS was disabled between 17:07-17:21. However, this would still not definitively place it before the 17:19 last transmission.