Deadwood was done in the sense that each season followed a set time frame, and the follow on movies were going to loosely cover the same folks but in much longer time spans. Not sure exactly off hand, but Movie 1 was supposed to be ~10 years and Movie 2 ~30. It has more to do with the railroad making its way out there. So, Deadwood S3 was done in the sense that it ended the same way Deadwood S1/S2 ended, after a set time with the mindset that there would be significant gap in story time before it was picked up again. In essence, it was as wrapped up as it was going to get. They could've edited in a "where they are now" title card to the beginning of the credits without changing the impact to the season/series.