Hi,
In the interview, they didn't ask me what my future address would be, but they did ask me where I would go first. I told them New York, but I didn't have to provide a specific address (I didn't have one anyway). I think that they understand that as I wasn't currently living in the US, that I would'nt have a residential address there yet.
For me, the only address that was important during the whole process, was the mailing address for the green card. This was required both on the application form, and I was also asked at the Point of Entry, when I first landed in the US i.e. they just asked "Is the mailing address that you gave on the aplication form still correct", and I just said yes.
The only other point was on the flight over, they give you those cards to fill out on the plane (they give them to everyone). One of them asks for your address in the US. I just used the address of the hotel I was staying in.
Regards,
Breandan.