It was recently released that Kaladesh (chandra's homeplane) will be the set after SOI. The two sets on the plane being "Kaladesh" and "Aether Revolt". So far this is the only official info we have on the sets:

I'm already a big fan of Saheeli, for many reasons

EDIT:

As I said in the spoiler room, I'm glad to see us going to steampunk India, but am very sad that I'm going to have to look as ugly computer generated gold for half the year.

As for theories, maybe Chandra will go visit home, maybe the new 'Walker Saheeli will be an aether adept on the Blue side of things and be part of the tyrannical government. Chandra will lead a resistance and maybe get Gideon to help as he seems like a solid candidate to toss in as Gatewatch back-up.

Maybe it was built from the remnants of a Persian-inspired multiplanar empire and they have to deal with an evil priest-like person trying to bring it back.

Surprised to see the walker so much earlier than any information. Shame Kaladesh is going to have to try and explain why everything looks and feels like Etherium without being Etherium.

Also, finally a bloody plane where we can see Tezzeret. Stupid theme preventing him from having any presence.

I am hoping for a non fair skinned female walker, although I would've wanted something akin to Koth's skin tone, Saheeli Rai is fine too (Southeast Asia re-present!)

I cannot wait for this set's arts...

Yeah, I'm generally okay with this.
Kinda hope Chandra just... Isn't here.

I'd love to see Tezzeret coming back into the fold. He can crack jokes about Kaladesh's metal being an etherium knock-off. Plus its been too long since we had Bolas involved. Tezzeret can use the McGuffin from Kaladesh to bring the Tyrant of Tarkir to heel, praise be to Emperor Bolas.

That is some absolutely adorable naive hope you have there. Shame you're gonna be wrong.

Yeah, you're the one fawning over Tezzeret.

I'm just sad that she isn't mono-green. There hasn't been an awesome green neowalker. Garruk and Nissa had potential, but they squandered them.

At least hoping for the **** ARTIFACT WALKER on an artifact plane has some basis in reality. Thinking a Gatewatch member won't be on their plane is sheer madness.

And yet Chandra isn't front and center...

But hey, maybe we'll get Daretti!

Just a heads up, the new "Intro Product" will release the same time as Kaladesh. They will feature two planeswalkers per set and each of the four decks will utilize two colors. This is the image they used to show off the announcement:



Expect Chandra to come home.

Who knows. Pure-artifact is strange, but maybe Creatve can be CREATIVE this time.

Also Persian multiplanar empire.

Hrm, not thrilled with tossing alternate colors at the mono color Walkers, but on the other hand, easy access to walker cards.

Plus I've been kind of pissed that the duel decks are all faction based. Which haven't been terribly good.

While it will be easy access to 'Walker cards, I'm not entirely sure if they will be good cards or not. MaRo said in his write-up that they will be splashy and high mana cost, but simple enough for new players to follow.

Like, I don't know if the specific 'Walker cards in those specific decks will be the same as the ones in the block they are meant to be legal with. Honestly, the announcement was confusing as hell.

They will not be:
The mythic rare planeswalker is one of the five categories of deck-specific cards. (The other four are the rare tutor, the planeswalker-enhanced uncommon, the planeswalker-flavored common and the appropriate dual land.) None of those will be printed in the accompanying large or small set, but all of them will be Standard legal.

Yes I saw that, but it means that Wizards plan of only having 15 'Walker cards in Standard at any one time just went way out the window.

Now you'll have five 'Walker cards per block in the sets themselves and four less-good 'Walker cards that are part of the Intro Decks that are standard legal per block as well. That means Standard will be very bloated since there will be three blocks in standard at any one time.

It's been strongly hinted that Crucius the Mad, the sphinx who developed artifice on Esper in bygone days, was a planeswalker. My headcannon is that he was from Kaladesh, unless it turns out that Kaladesh has no sphinxes or we get some backround info on him in return to Alara.

Chandra: Jace, Kaladesh has a Sphinx problem!
Jace: Why do I feel like I have experience handling Sphinx problems? I should go with you to explore this mystery!
Liliana: Dammit Jace, this veil problem isn't going to fix itself...at least not in a way anyone will be happy with!
Gideon: Jace, it's been like months since you've been home. Aren't you like the living embodiment of law on Ravnica?
Nissa: Well I'm not going, I have a garden to tend to....for Zendikar!