You have a cat, you both are going to be working more and you have an allergic roommate? I'm sorry, but are you sure it's a good idea to get a second cat?
I understand it looks like choosing between two evils here, but I'd ask you to reconsider. I'd definitely wait till the move is complete. Moving is already stressful for a cat, I doubt it will be easier with two. A new cat takes some extra time and effort too, which you may not have available with both of you going to work more.
Besides, what happens when the move doesn't go through for whatever reason? A lot can happen in 6 months. I wouldn't take the risk. Find a different approach to keeping your cat happy, there are plenty of cats that don't have an animal friend yet are not unhappy.
If the cats have significantly more room at your new place, them getting used to each other will actually be easier after the move than before. After all, they have more territory so won't be forced to be close to each other all the time if they can't stand each other initially.