Mr. Laser Beam wrote:
Or maybe that mission never happens and as soon as the Narada exits the black hole Data's head disappears from the cave.
Not possible, since the prime timeline still exists even after the Narada
goes back. It creates an alternate timeline which branches off from that point, and which does not overwrite the existing one.
And since it is highly unlikely there will ever be an alternate Data (due to the butterfly effect), then in the Abrams timeline, nobody will ever know whose head that is.
There can't be a Data-head in a cave in this timeline. None of the time-travelling that happens in TOS, TNG, DS9 and VOY will ever have happend.
The Narada arrived in a universe/timeline that was already different/changed because of her arrival; the changes "rippled" back in time before Nero and his crew caused any changes because their actions prevented all of the time-travelling we've seen in the other shows movies.
The universe/Federation/Starfleet that is the home of Kelvin and her crew is/was always the world that happens/would have happened without the interference of our oldTrek heroes.
God, I've watched too much Doctor Who.