Alright, I've got it. Guessing the ending for BP may be difficult, but it will have one quality for certain...
It will be insane.
Battuta says it has to do with a hint present in every mission which is literally staring everyone in the face. Well that can only mean one thing. The constellation Orion. Sitting far off to the side embedded in every single mission's skybox.
Oh how prey tell does Orion fit into all of this? The name of a grandiose Freespace destroyer also the name of a constellation, also the name of some ancient Greek warrior? Well you just keep reading.
Admiral Byrne says the UEF has no chance by winning this war through force of arms, and I believe him because the Fedayeen have something mad in store for the Tevs.
You know who Samuel and Father Bei are searching for at the ending cut scene? Shivans. That's right... they are calling the great destroyer to unleash damnation upon their foes at the risk of civilization itself.
And lest we forget Orion, the iron fist of the Shivans plan to obliterate the failed human race with apocalyptic doom. The Shivans set each of Orion's stars ablaze in a supernova chain reaction while slingshoting the fiery masses of destruction towards several worlds throughout GTVA controlled space by using the gravity of black holes. The Terrans are decimated and plea with the Fedayeen, but it's too late for both of them, because neither one is in control of their fate any longer.
The Shivans invade and do what they do best. They eradicate Terrans, Vasudans, UEF forces... all life must be purged. The GTVA UEF coalition of the damned are helpless to stop the Shivan threat which encroach upon their systems through both time and space. Using newly upgraded 'youcannotgetawayfrommenowsuckers' drives.
Thousands.... no wait... millions no wait... countless Vishnan warships emerge to bring balance to this otherwise impossible and reckless foe, for what is there to preserve if life does not exist. The physical plane of space is overwhelmed by the endless number of consistently warping ships such that the universe fragments into infinite dimensional planes of existence and space as we know it has morphed into continuous vibrating wavelengths of energy, without position and without dimension. Subspace is not subspace and time is not time. A broken equation, an ultimately incalculable scenario. The Vishnans have completed their task of preventing the universe from going off balance because an undefined equation can never yield 'false'.
You were worried about supernovas? Well prepare to be blown into the next universe, because this primal form uncontained energy is the recipe for a second big bang. A universe reset.
Boom.
Billions of years later, every subatomic particle falls into its rightful place and events take their course, moving and shaping themselves into fantastically an exact copy of the previous universe. Time manifests the events of the second universe right up until the point where the war in heaven begins. The Vishnans saved the universe, the first time... Will it happen again?
Yes because this time the GTD Imperiose fails to jump in and the GTD Cartheage gets destroyed.
I know, I guessed everything. Call me Sherlock Holmes.