Dunkmaster Darius
presumably still in the works. Last we saw was this video showing off work in progress animations and a model.
Sion Rework
Very involved and long process as his art and gameplay are being totally redone - basically making a new champion but being gated by what players already like/know about Sion. Still in the works.
Lifetime RP
Still in the works, last update was earlier this year and they said :
"Our initial thought on this back on 2012, was to give our fans different Summoner icons, but that was at a time when icons weren't readily available and as Lavasioth pointed out - icons won't do."
Baron, Dragon, Map Rework
These would likely all come together. A map rework for Summoner's Rift, the default map, would be a massive undertaking and definitely be something they spend a hell of a lot of time on. If this is what their doing, I feel like they would save everything for one nice package instead of putting a crazy looking baron or dragon in the middle of the current map.
Pizza Girl Sivir
This was an art demo, something very clearly marked as "not a promise". Usually don't expect to get updates about them.
Replays
Currently on ice since the servers couldn't handle the stress.
The last official statement about them:
"WE ARE NOT CANCELLING REPLAYS! The big problem we're still facing is that we need to make sure every region worldwide has servers that can handle the strain before Replays can be released. Taking them offline for a while gives us a few more options to explore in terms of getting to where we need to be (such as adjustments to how our servers might need to interpret or access Replay data). You can expect Replays to return to the PBE further down the road when we're globally better positioned to support them. "
EDIT: Here's the pie analogy that /u/Pwyff is known to give:
"Off the record (lol) my understanding is that replays are still in the garage. The way someone explained it to me (analogously):
Under the regular strain of games we're still trying to keep up with our load demands (buying equipment fresh out of the factory, moving to bigger data centers, etc). Adding a replay system where players could get all of that information on their game would exponentially multiply our traffic. If the feature proves popular, you're essentially playing the game once for 10 people, then playing it again for all 10 people individually as they download all of the information of the game.
Very loose analogy, but when you get to our levels of scope you hit some pretty weird situations that most haven't considered. It's like saying "this recipe makes pie for 20" and everyone's like YEAAAAH THAT'S A LOT OF PIE. But imagine if you're making pie for 1,000 people. Now you're like "JUST TAKE THE RECIPE MAKE IT x50 RIGHT," but then everyone's like "BUT WHAT KIND OF OVEN CAN TAKE THIS!?" and then electricity comes into play and pie tins of incredible scope and even finding fresh filling to fill all these pies and it's complicated man."
Ao Shin
Meddler commented in April that Ao Shin is still quite a ways out:
"We're still working on Ao Shin, but for now he's a long way out. Some of our initial ideas for translating his concept into an actual in-game champion haven't quite panned out, so we're continuing to work towards an approach that really hits the bar. He's definitely a champion we want to make happen, but we'd rather take a long time than fail to do his concept justice."