in the new raiden trailer his name has been changed to khan
I'd say the raiden trailer is more recent. They probably changed the spelling to avoid association with ShaoSo, you say "Kahn" And "Khan" mean the same?, damn, i didn't noticed this change of name until now you mentioned it :O, my guess is that is a mistake, considering that the health bar and the videos where the selection char screen was shown, the name was "Kotal Kahn" IMO that is more canon than some type appearing on a trailer, good observation bro.
And why would they want to do that?
Hence the exact same reason why they changed a certain dreaded MKA character's name from Kublai Khan (who was an Ancient Mongol WARLORD) to Hsu Hao.