How would they determine which network/venue showed which version? They couldn't just transmit it to random stations with a fifty-fifty chance of either one showing up on any given television, because that's not how television transmission works. I suppose they could have one version on television and another on Internet livestreaming, but the former would probably massively outweigh the latter, and the gimmick would be not only lost, but figured out almost immediately.
And which would be canon? Both? It couldn't be both, because the retroactive resurrection of the Time Lords means that they will almost certainly be showing up again in future seasons, especially since Gallifrey not being blown up means the Master is still alive, while destroying Gallifrey on-screen more or less voids all chance of seeing any Time Lords again ever, unless one or two TARDIS out in the last few seconds before the time lock hits and renders that impossible. And if it was decided to be ambiguous which was the canon version, then nobody would even be able to mention the Time Lords again in future episodes, because the Doctor's response to that mention would be radically different depending on what happened, and we'd miss out on one of the bigger parts of the Doctor's personal lore.
If that was a "just for fun" hypothetical instead of an "I wonder what would happen if they did this" hypothetical, then I apologize for ruining said fun.
Oh, and speaking of retroactivity, Gallifrey not being destroyed finally closes a plot hole in the "You Are Not Alone" reveal from Ten's era. Namely, how would the Face of Boe have known about the Master?
It was presented as though, despite the Time Lords travelling across all of time and all of space, the only "actually alive" ones left were the Doctor and the Master, the latter of whom was disguised as a human at the end of the universe, hidden in such a way that not even the past selves of the Time Lords couldn't detect him. How would the Face of Boe know he was there? We can't say that he would have had information from when the Master was running around Earth in the 21st century, because all of the Master's activity was wiped from history when his paradox machine was destroyed, which also wipes out all possibility of the Face simply remembering that information from his time as Jack Harkness(if we're going with the Jack-is-the-Face-of-Boe route here and not the the-Face-of-Boe-is-a-member-of-a-different-species route), since Jack was the one who destroyed it and was right next to it when the temporal reboot happened, so we can't say he would have escaped its effects.
But, if most of the Time Lords are still alive, the Face wouldn't have needed to know about the Master. He could have just heard about the true fate of Gallifrey at some point in his long, long life, as well as the Doctor's belief that Gallifrey was destroyed, and then tried to use his last seconds to tell the Doctor what really happened. Of course, all he got out before his death were four cryptic words, but that falls true no matter what he was talking about, whether it would have been a warning about the Master or a message of hope about Gallifrey.