With more effective hauling, dwarves will have more time to spend on productive working. This means they will produce more. But we already have an overabundance of items in fortress mode, and there's so many of them that many items become virtually worthless (for the player, that is). Is this something you have given any consideration to? Are there any plans to reevaluate item abundance, and if yes, what are they? Changing job speed, implementing economy, making items break...?
Yes. Fortress Mode Econ will be eventually getting redone during these Caravan Release. And that will probably touch upon item creation, skill increase, raw materiel consumption.
Release 4 (Particularly Inns and Fairs), Release 5, and Release 6 for Fort Mode integration. Release 8 may also see dorfs using their items differently, possibly even 'consuming' items and tossing them into the bin. Though the personality rewrite is more about having villains and motivation for Necromancers and Wars for the Army Arc.
And during these releases maybe well also see Improved Farming, Fortress Subgroups, (Their demands could totally eat up Forts excess goods to some extend), and Improved Mechanics (which contains a rock crusher on the wish list and it'll also give us more things to use for making forts and for maintaing forts.)
And Toady One has touched upon items breaking done more consistently and universally in Fort Mode, but as we've seen with clothing, that just apparently create lots of issues.