There’s more money in a replay at the Emirates than there is in a trip to the Etihad. Not just because it’s a bigger ground to begin with but because Arsenal would fill it whereas City really struggle even in the lesser Champions League matches, let alone domestic cups against lower league clubs. The tickets would also be way cheaper in Manchester. City played Burton in the League Cup semi-final 3/4 years back and only got 32,000 in.
There are more important things to think about in the meantime, such as how the hell is the chip shop going to cope.