Here's what I'd like to accomplish...
1. Create a "Today" column that is always limited to a maximum of <n> cards
2. When an <n+1> card is added, the bottom card would be moved to the top of a "Backlog" column
3. When the "Today" column has <n-1> cards, the top card in the "Backlog" column will be moved to the bottom of the "Today" column.
So, essentially, the Today and Backlog columns _together_ will act as a queue but will never display more than <n> cards in the Today column.
Possible in Trello?