Fees will go up if micro payments will come into the play... equilibrium will be found... fees influence transactions size and vice versa.
Micropayments are great. You get more of them in, you get more profit on your block.
The cost to write to the block is trival, and if you ignore a transaction because the fee is too little (but worth more then the cost of adding to the block) then you leave money on the table.
Remember the cost to mine the block is sunk cost at the time of transaction writing, so it is irrelevant regarding the fee you are willing to accept to write a transaction.
Fees will stay low unless there is collective action (cartel) to prevent them from being low. Then someone will come along outside of the cartel and sweep in all of the transactions that have been sitting around with little fees and profit majorly from it.
Mining power will decline (in investment & energy use) to match the payout + total fees per block. They are all slaves to a race to the bottom unless individuals (such as pools) use their power to force fees higher. Transactions that aren't urgent will always be able to use low fees and just wait around for someone to scoop them all up.