It was proposed for new testnets to make it like that. And I agree with Garlo Nicon, that it is better to not touch the limit, but change the proportions instead, by mining enough coins for developers, before releasing new client for new testnet.

Also, when it comes to OP_RETURN, then there are other limits, which will still make things stable. There is a Script size limit, a transaction size limit, a block size limit, a transaction fee limit, and so on. And when OP_RETURN limit can be trivially bypassed, then it can be lifted, because it does more harm than good.