2000 commons as an upper bound is nothing. There's like 8 million of each of the recent reward commons, 125k of their gold foils, millions of each rare, etc. and that's before even considering other sets like CL/RW or the hundreds of millions of other cards that will inevitably be printed in the future. Having only 5 slots per land would be completely absurd. I need a reason to buy another 500k cards, not a reason to start dumping them.