OK fretful cupcake, because Bitcoin is antifragile, you can stop worrying it won't "remain usable."   

Blocks should scale up by representing more valuable transfers.  Blocks need to grow vertically, like skyscrapers making the best use of precious New York financial district real estate.

They don't need to, and shouldn't, sprawl out horizontally just 'because cheap hard drives.'  This is the difference between mere growth and actual development.

Blocks should be optimized, not subsidized.

Removing the 1MB constraint removes the incentive to optimize and subsidizes inefficient usage.

Not to mention the pernicious effect of excluding TOR/DSL/etc. and confining the BTC system to high speed connections and clearnets.

To "remain usable" in the event of ISP/.gov crackdowns, blocks must remain small enough to keep the network defensible, diffuse, and resilient.