Something like this would be major. Traditionally, auto manufacturers would have a summer shutdown where the lines are retooled for production of the next MY. I seem to remember some retooling and "line 2" work going on before the "D" announcement, so 2016 Q4 would be a good bet for a significant facelift.
However... changes to the bumpers, nosecone, front lights and interior (seats) could theoretically happen without retooling the line, so could be sooner.
However... changes to the bumpers, nosecone, front lights and interior (seats) could theoretically happen without retooling the line, so could be sooner.