Today we 'finished' my ongoing campaign, started in 2003 when my wife and I had just started dating (cue: AWWWWW).
We'd been moving toward this for a while, but when it came it was sudden, intense, and somehow over before we knew it. The players were asking "what's next?" and "what about items? XPs?" before realizing... oh.
What's next, after a campaign you've been running for 9 years? A break, for one thing. Also a thorough weeding of my working D&D directories for Scrivener projects, notes, character and NPC sheets and anything else not of global gaming significance. A cleaning of the slate after years of haphazard yet painstaking world building.
My next campaign will necessarily be different. If I pursued a campaign in the same setting I would (and do) feel compelled to advance the clock a few centuries at least. I have a few ideas along those lines.
A. Let the players pick their characters' futures. What are their long-term goals now that the BBEG has been defeated? What would they like to accomplish? How might their goals change things in the future?
B. Mix things up. This was a high-magic, morphing-geography, localized-religion setting. Magic items are available to those with money in fairly large metropolitan areas. I've no experienced the full effect this can have on a campaign from bottom to top, from 1st to 15th levels. My next campaign may have low-magic or self-made only.
C. Rules refinements. Lethality. It's something that is sadly lacking in Pathfinder. Buying extra hit points with feats and leveling options, death at negative con in hit points, and lacking overall any penalties for dying. I've added a few layers of complications to the rules and find that there is still more room for consequences in the rules system.
More D&D, different stuff, more sand boxing. That's what's next!