I can confirm that when I completed the final mission for the Sol expansion campaign series, which did in fact secure the known galaxy under my galactic iron rule, I was then presented with a (frankly rather late and redundant) credits roll.
I patiently wiled away the time waiting for the credits to finish by mining some nearby asteroid belts.
Finally, my patience was justly rewarded with a special post-credits cutscene.
There was a blinding flash and I watched with amazement (and perhaps a smidgen of wet dribble in my underwear) as the nearby local space was ripped apart by a ferocious tear in the space-time fabric.
As I peered cautiously beyond the crack, covering my eyes slightly from the blinding light, I was able to catch sight of a hulking black and green ship mass, biological in nature.
Panicked by this, I hauled my Anaconda into gear and fired the thrusters to escape as a deep, rumbling, gravelly voice uttered...
"SOON*...."
* Registered trademark. May or may not actually imply soon in the literal sense, but more in the philosophically intangible sense of the word...