Are your concerns more to do with the future when block reward becomes an insignificant incentive compared to tx fees?
Yep. But it's also not clear what will happen if there's 20 MB space available
and there's enough "dust" transactions to fill it.
Would they? Why not? More money, might outweigh the costs for miners if fee/byte is high enough.
But everybody else won't get that "fee/byte" profit, so they will "pick up the tab" in a sense.