If I'm creating the gaping hole that will exist if I don't have Julio, I've got to have TWO players that are realistically capable of filling holes by 2018.
This is sound reasoning, but only if the goal is to compete in 2017. If they plan on punting in 2017 then it makes sense to trade Julio's present production for the future production of a younger guy.
I'm still on the fence about whether or not to punt 2017. It all hinges on how well Albies and Swanson progress the second half of this year. If they don't show they are ready for MLB action in 2017, then nothing the FO does can make the team competitive next year. If that's the case then it makes sense to trade Julio's "now" for someone like Bregman's future contributions.