What happens next? I’m not sure why the show was cancelled but in your minds eye what happens next. What becomes of our happy characters and the “camp” of deadwood next if you finished the story?
I don’t know, but I was very upset about that. It took me a while to like the series but I thought it definitely had another season in it. I read elsewhere on SDMB that it was canned for production costs. I don’t get that unless they’re talking about actors’ salaries. Period costumes shouldn’t be an issue. We’re not talking 17th century French nobility after all.
I believe the fire that destroyed much of the camp (including the Gem Saloon) would have been the focus of a fourth season. It occurred in 1879, so the timing would have been just about right. Damn you, HBO!
We would have found out if Al had finally authorized having cinnamon for the canned peaches. 
We probably would have found out more about the acting troupe. They were a distraction in the third season, but would likely have been fleshed-out more in the next season.
Well, period always does cost more - just because it’s dirty doesn’t mean it’s cheap! But I remember hearing at the time that they cut it because they didn’t want to cut Rome, another expensive (and while fun, inferior) show.
A few thoughts of my own. I find it very odd that HBO would cancel this show after setting up an epic cliffhanger of all times at the end of season 3. Also always wondered why Trixie didn’t go to Dan or Al and get a real gun say like a colt .45 to shoot Hearst with instead of a frickin derringer. Also with as many sociopaths as there are that call deadwood there home how is it that Hearst has stayed alive this long with as many enemies as he has made? He’s quite wealthy and powerful but he is after all only one man. His neck cuts as easily as everyone else. But wondering if Al approved of Jewel serving cinnamon with the peaches at one of the town meetings has kept me up at night! Damn you HBO!