They will never be finished. As soon as this is "done" they start on part two. I wonder if they will do another kickstarter or if they already made enough to find the next one…
Iron Lore - er, Crate - has not behaved that way in the past. You're entitled to your prognostications, obviously, but they're not exactly data-driven.
Their next project is a big question mark. But they expanded Grim Dawn far beyond what was envisioned in the original Kickstarter campaign, and the pace of development has been super-slow (even tho very steady) - it's hard to imagine they'll do even more with this particular game.