Keeping 2020 in mind is NOT the same as resting on laurels, andd the fact that so many key players are free agents after 2019 is more of a reason to keep 2020 in mind than it is to just worry about it later. My guess is Dombrowski plans on having a job then, too.
If the goal was solely 2019, why Eovaldi over Kimbrel? Eovaldi was only with the Sox for 12 starts and 54 IP - hardly numbers one would associate with a core starting pitcher.
The answer very likely he was brought back with not only 2019 in mind, but also 2020 and beyond, as Sale and Porcello could both depart.
Kimbrel might return still. But not with a contract that Dombrowski figures to hamper his ability to re-sign Betts or whoever. I do think he knows what he’s doing and his plan isn’t simply 2019 and then “see what happens.” Because he knows that if the team sucks in 2020, no one will say “Yeah but we won it all in 2018, so it’s ok.” Just like no one said it about Cherington in 2014...