I haven't had a TPK in a while (and the last TPK I had was quite intentional, ending one "chapter" of the campaign, and beginning a new one, with players playing their former PCs as "wandering souls"). However, after a typical TPK, I'm likely to scrap that particular campaign, come up with a resolution to any important story threads, incorporate those events into my campaign setting, and move on to a new campaign, likely in the same world, but in a completely new and unexplored area.
I've been running a "persistent world" for some 10 years now, and events of one campaign always touch upon the events of another, but I do not consider all that to be a single campaign. Instead, it's a shared world experience with established continuity.