If these are the only two options, I �d go for the first one (will go to London).
You don �t �travel to London � for a job. You go to London, commute, move, etc.
I agree with Apodo, Almaz and others that it �s a poor question and that other options would be much better, such as
He �ll move to London.
He �ll be moving to London.
He is moving to London.
He �s going to move to London.
BTW, I think the question isn �t really correct either. I �d write
�John got a new job in London, so he ________ to London next October �.
No need to split this into two short sentences.
