Wow, I can't even imagine ever doing everything. Not knowing what you have done, here's part of my 'things I want to do that I haven't done' list. Maybe there's something on there you haven't done yet.
A Wishes cruise
An Illuminations cruise
The segway tour
Keys to the Kingdom tour
The new nemo ride
The new nemo show
Be picked as an extra at Indy
Be picked as an extra at the backlot tour
The early morning safari that only guests at AKL can go on
Concierge at the Poly
Getting a tent and camping at Fort Wilderness
Chefs table at V&As (who am I kidding, ANY table is fine)
Maelstrom (we always end up skipping it, no idea why)
Drink my way around the world showcase (all grown ups trip planned soon

)
Lead a parade
Go to the waterparks (too busy with the theme parks so far)
play mini golf
rent one of those zippy little boats
Be able to spend so much time at WDW that I can sit at an outdoor table in France and eat pastry and drink champagne and people watch for hours without feeling like I should be doing something else (like riding Maelstrom)
See the Cirque de Soleil show
Stalk the dream team until they give me a night in the castle to leave them alone.
Have the money to do crazy things for other people - like hang out at the TTC and buy tickets for them. How fun would that be?
Go to the Adventurer's club (that all grown up trip can't come soon enough)
Go to the campfire at Wilderness lodge, roast marshmallows and make smores while watching the movie.
Then again, there's still 'normal' rides I haven't ridden and 'normal' shows I haven't seen so my whole list is pretty long.
If you're "all parked out" then exploring the resorts might be fun. Nearly all of them have some sort of activity (or actvities) that are fun and unique. Even just checking out all the transportation options to and from the resorts (we took the boat from POR to DTD and had a driver who was a beatles fan, he replaced the 'standard' music with some beatles hits and the whole boat had a beatles sing along down the Sassagoula - what a hoot!) the boats connecting lots of resorts to each other and to the parks are fun just to ride.
Tea at the GF, the gueyser (spelling?) at Wilderness Lodge, lounging on the beach at the Poly with a frou frou drink (I really need to check the dates on that all adult trip), riding bikes around Port Orleans - there's a whole list at every resort.
Downtown Disney is great. We had a ball at DisneyQuest and watching the kids race legos at the
lego store and trying to appropriately stuff a mr potato head box and Ghirardellis - moment of silence for Ghirardellis - it would take me three or four nights just to feel like explored everything down there.
I know...take me with you and you can experience the joy of watching me do all the things you've already done!! I'll be entertaining, I promise!!!
I know you'll find some stuff to do. If you find you've really done it all then my advice would be to do it all again
