I feel like if it's actually on Sam, he would have to bring up Marky as his ace-in-the-hole to justify its' existence whatsoever. He has been deathly terrified to even utter Sam's name for so long - if he's actually reviving Content Cop after years of saying he never would, and then is aggressively dropping the video on his birthday, then surely it has to be substantive enough that he actually feels genuinely confident for making a show of hyping up the return.
...or, the Sam birthday thing could be a complete and utter unintended coincidence, and the video will be about Elon Musk. Who knows!