This has been discussed for a while.

I used to support the idea of an algorithm to recalculate the limit, as it's done for the difficulty. But currently I just think miners should be able to create their own limits together with multiple "tolerance levels", like  "I won't accept chains containing blocks larger than X unless it's already N blocks deeper than mine". Each miner should set their own limits. That would push towards a consensus. Miners with limits too different than the average would end up losing work. The point is that like this the consensus is achieved through "spontaneous order" (decentralized), and not via a top-down decision.

That said, I do have the feeling that this change will only be scheduled once we start hitting the limit.