You are speculating. If Bitfury's next chip design is not compatible with the chained design of the existing chips, then it's not going to work chips/cards/minit planes etc. How about wait until Bitfury actually announce a new chip design before continuing with this type of discussion?
It's not entirely unreasonable.
He wants to know if he will be able to upgrade his existing miner with new daughterboards.
It's quite possible this could be the case if Bitfury uses the same hardware interface (pinouts), even if the chips are designed to work completely different.
You are of course right that there cannot be any guarantee of this at this time unless Bitfury himself commits to a future interface.