Honestly, I just think the writing is on the wall: once quantum machines get big enough, the math behind today's encryption stops holding up. Maybe the other side is right that it takes time, but a decade feels like plenty. I can't prove it, though.
Isn't it just obvious that once the hardware gets big enough, the old encryption crumbles? My opponent makes a fair point about it taking time, and honestly I can't argue the details. I just feel a decade is enough.