I have one 3DS and would like to transfer a Pokémon from XY to ORAS, but don't have access to the Pokébank at this time. Is there any way that I can do this?
Simply, you get the pokemon you want to transfer and go onto the GTS (Do not put a legendary in it)
Next, you put a bad pokemon in the GTS and ask for the pokemon you want to trade. Make a message that will stand out to you, then make its restrictions fit for the pokemon your trading. Send the pokemon to the GTS. Save after that. Go to the home menu and close your game, Swap the game from XY to ORAS (Or vice versa)
Then, go back onto the GTS in the Other game and look for the Bad Pokémon you sent. Once you find it, trade the pokemon that you asked for. Save
And there you go, you have transferred your pokemon.
A better solution is to use 2 consoles, one with XY and the other with ORAS and simply trade all the Pokemon you need. (Of course with the help of a friend, if you don't own another console.)
That's faster and definitely safer than putting them on GTS. There are more "thiefs" than you think, trust me.