If the number of people that can afford to put down 20% has shrank significantly over time, won't the pool that can put 3-5% inevitably shrink as well? Will we

If the number of people that can afford to put down 20% has shrank significantly over time, won't the pool that can put 3-5% inevitably shrink as well? Will we return to 0-down homes? Where are down payments terminally headed?