What you are not adding in your "story" is the following. When the Lightning Network is implemented, most of the micro transactions clogging the network at the moment, goes off-chain and this leads to a reduction in the miners fees.

Even with the LN the Mempool will become congested again in the future. and then the Block sizes can be increased to manage that.

Everyone seem to think, the Block size with the LN, should be fixed, but it is not the case.