This is my take on what happened after Optimus died. Do not fret. I'm still doing more for the series. This isn't the end.
It was the oddest sensation seeing the blade jutting out from the front of my chest. I didn't even feel Megaton's blaster when he fired it. I didn't want to believe it was happening because it meant that I failed. I failed my fellow Autobots and the countless lives of this planet.
So as I was dying I did the only thing I could do…I told Sam to run.
When I opened my optics I only saw shadows approaching me in a misty haze. I collapsed onto my knees and wept. I could sense who they were. I didn't deserve to be in their company in life and certainly not in death.
I was weak. I failed. Everything I did in my life was a waste. And now an entire world, so many innocent lives would perish because of my ineptitude.
"Your life is not a waste, brother."
"Nor are you a failure, brother."
"I am and now billions of lives will die," I wept, keeping my head bowed down.
"Everything in your life has a purpose, a reason," another Prime said.
"Even your death," another added.
"I do not understand," I said, looking up to see so many Primes of the past standing there.
"Youngling, no one understands Primus' will," one of them chuckled.
"Rise, Optimus," another spoke as he separated himself from the others and approached me. "It is not your time to join us."
I looked quizzically at him not understanding what he was saying. It was then that I felt a strong connection to him. An overwhelming sense of pride and love filled me from within. He smiled, resting a hand on my shoulder.
"You have done well, Optimus. But you must go back. The Fallen must be stopped and only you can do it."
"I don't understand. How can I go back?"
"How is not important. It is your destiny. You still have so much more to do…my son."
Before I could respond, a flash of light engulfed me, blinding all my senses.
Then I felt the pain in my chest, the sand beneath my body, the sunlight upon my face. Explosions sounded. Voices were telling me to get up. So much was happening all at once I hardly had time to process it all.
I reacted instinctively to the situation as I've always done when thrown into the middle of a battle. I was able to focus on the task at hand and get it done. It wasn't until much later that I had a chance to process everything…my death…my rebirth.
It was well past sundown and I still stood at the edge of the air craft carrier, gazing up at the stars. For the first time, in a long time, my processor was at peace. One burning question that had always plagued me as I grew up was finally definitively answered.
My father was proud of me.
Of course, I had to tell Ironhide and Ratchet they were right despite the flack they gave me for being a silly youngling. Time and time again whenever I had doubts they would often reassure me that my father loved me and that he would be proud of all I'd done.
Now I know.
My father does love me and he is proud of me.
I still had so many questions I would have liked to ask. Questions only my father or the other Primes could answer.
"In time…my son…in time."
I smiled hearing my father's voice within, feeling the power from the Matrix surging strongly near my spark then slowly ebb away. My spark had felt that same energy before, just after the battle was over. The pull within my spark had compelled me to climb up that pyramid all the way to the very top.
Upon inspecting the damage I saw that the Matrix of Leadership had not been destroyed. It had simply transformed.
"Optimus, what are you doing?" Ironhide asked over my communicator, startling me into pulling my hand back from the soft blue glowing orb my optics could not look away from.
"I'm making sure the device has been permanently deactivated. We cannot afford to let such a weapon fall into the wrong hands…human or Decepticon."
"Understood. Hurry it up. You know how cranky Ratchet gets when you're injured."
"I'll be down momentarily, Prime out."
The orb pulsated brightly as it slowly rose up before me. I felt surprisingly calm when I took an involuntary towards it.
It was calling me.
The pull on my spark was so strong now that it caused my chest to transform, exposing my spark chamber. In a flash of blinding blue light, the orb rushed at me. The collision with my spark chamber caused me to jerk back and lose my footing. My father's voice filled me within as I lost consciousness.
I smiled, looking down at my chest, recalling how Ratchet told me I made a spectacular klutz of myself by falling and bouncing all the way down the pyramid. In private, I told him what had happened and he confirmed what I somehow already knew.
The Matrix had fused itself to my spark chamber, becoming a part of me.
Standing here, I now remembered what I head as I lost consciousness.
"You are no longer just Optimus Prime. You are the chosen one…the bearer of the Matrix, a source of power and knowledge that only you can control. Use it wisely my son for it is your destiny."
"I vow to do my best, father," I whispered to the heavens above, knowing that he's watching over me.