I don’t consider alternate history as such to be a branch of time travel, and in fact I don’t consider it to be science fiction, or even fantastic fiction as such.
On one hand, it’s time travel fiction if you create the AH by traveling into the past, or sending a message there, or if the future sends a message to the present that creates a different future.
On the other hand, it’s science fiction if you can travel to the AH by using a sideways time machine, or a psionic ability, or other things of that sort. (If the alternate worlds don’t originate in a historic divergence, or there isn’t a metric for how far away they are, because they differ qualitatively and not just quantitatively, that’s not AH. If you get to a different world by magic or divine intervention, that’s fantasy rather than SF.)
On the third hand, nearly every work of realistic fiction is set in an alternate reality that implies some measure of AH. This is really obvious with, say, Babbitt, set in the fictitious city of Zenith in the fictitious state of Winnemac, but considered a quintessentially realistic and mundane novel. But the same could be said, on one hand, about Ruritanian novels set in invented small countries with no overtly fantastic elements, and on the other hand, about novels such as Pride and Prejudice set in British country towns that never actually existed. These are asking “what if?” just as much as the essays in J.C. Squires’s collection If It Had Happened Otherwise are doing so.
But with these strictures, I’m asking specifically about the creation of an alternative future by time travel from the future to the present, which IS SF and is at least close kin to AH. I don’t think AF is literally AH, because stories about the future aren’t historical fiction, but it’s something very close. What do you call this?
Maybe “averted prophecy” or “averted future”?