Well, according to my signature it's not time to panic :rofl:
The 5GT and the Z4 (last two remaining models on longest production run) are both still running on their internal designators first introduced in '09. Historically, 9 year production runs are not abnormal so we could see the F07 through the 2018 MY. I would only begin to question abandonment of the 5GT if BMW introduces a new generation Z4 with no announcement of the 5GT refresh.
On one hand I would be saddened to see production stop, but on the other it would be exciting to be an owner of an exclusive vehicle. It certainly would stabilize and potentially increase value, see 850 series as example.