Yeah, some mod or Dauroth as OP could put huge [SPOILER ALERT] tags into the the topic's title.
I forgot to put it in the title, but it's at the very beginning of the post!
[spoiler='SPOILER']I think that was not a clone! It looks like a flashback! If Mengsk planned the whole thing, he had to ensure his safety somehow, and this was one of the things he's done to achieve that![/spoiler]
There is a video that appears to be a work-in-progress of the ending cinematic (or so it seems so) from the second chapter of StarCraft II - Heart of the Swarm! If this video is legit, you decide! I personally think it is, since I can recognize Chris Metzen's voice for both Arcturus Mengsk and Raynor in it! Remember, this is work in progress!
Since there is probably no new music recorded, the video features music from the Transformers movies, despite the fact that they could have just used music from Wings of Liberty!