Hey! Great question
The core rules ($1) are what you got on DTRPG a few weeks ago.
The ashcan version ($5) are the core rules plus both existing dungeons AND the new city generation rules with all new original art (about 12 pages total)
The digital version ($12) gets you the ashcan now and the final digital version which will have even more content and be what goes to print eventually.
This one is, as you put it, the future of Down We Go.
We are still talking about how we will be implementing it on DTRPG, but it will be a new product there either way.
Please let me know if you have any additional questions