Is Nullius going to get updated to work with Space Age / 2.0?
If yes, will it incorporate new features like items stacking on belts, the new fluid mechanics, and quality?

It will be split into a separate version that supports the DLC features. The current version will be made compatible with 2.0, but with minimal changes to get it working, not optional new mechanics. New fluid mechanics aren't optional, so they'll have to be supported.

Awesome! Nullius was by far my favorite overhaul mod, really looking forward to playing it again with 2.0 trains!
Thanks a lot for all your work on this project!

+1 on this being great news. I have spent 1000s of hours on Nullius, and it's pretty much the only way I like to play Factorio anymore.

I'm very hesitant to buy the expansion because it doesn't look like it takes the game in directions I want to go.

As for the fluids -- I really liked the Nullius fluid system. Seemed much better than the original or the new one in the base game. As a fluids guy (Aero-Astro engineer), it was much more intuitive to me that fluids flow from high pressure to low pressure. The Nullius fluid system wasn't exactly a physics simulator or anything like that, but pretty much the fluids always worked like I expected them to work, which was the main thing.