The question came to mind today when Anima App released Auto-Layout, which is flexbox-like layouting for sketch:
This functionality was your main pitch in the Subform kickstarter video and in the follow-up medium article about pushing pixels.
Sketch now offers all what was promising about subform: there are overrides and datasets, flexbox layout, full atomic design possibility and clever techniques. Even states is covered, although they are not collected in one entity.
The Figma team works really hard and fast to keep up with sketch, their tool is really solid and usable.
Webflow is slower in keeping up but has released global swatches, a feature that was heavily requested via their new wishlist site. Also they still are the only design tool that offers creation in the medium of the final product. I'm excluding tools like wix, froont and pinegrow since they are not as advanced.
As I see it, the only thing that can be done better with drawing tools is better UX inside the tools for the designers. Maybe I'm wrong and adobe cracks hassle-free, direct export-to-production-code tomorrow, but I wouldn't bet on them.
A completely different approach are 'declarative design tools', as Jon Gold calls them. This article covers his thinking. A combination of drawing tool and rule-based declarative options is where I believe the near future of design tools is. Whoever comes out with the most usable solution first will be ahead. I'm sure you've read Viljami Salminen's article about tools and processes, a great read.
But back to my initial question: Where in this landscape do you plan to place subform? What makes it unique?