Some time to kill. I think I'll just rank the settings by how much I'd like to see them, and comment on the chances I think we'll get them.
1) Ravenloft. It's cool and we only saw Barovia. There's a whole world beyond that I'd like them to acknowledge, and there's room for new mechanics such as races, fear, subclasses, etc. Odds: Super low. It's been done.
2) Dragonlance. This got me into D&D. And the novels keep it popular. It's well known and not entirely generic. Odds: Medium, and tricky to boot. It's generic, but slightly different than the norm and the novels keep it popular. But the setting has really been hit hard by constant changes and tweaks from the shifting editions and game lines, and even the DL fans are divided on what they want to see.
3) Planescape. Simple setting of Sigil and ties into every other setting, making it something you can use without restarting a campaign. And its just neat. Odds: High.
Eberron. The new kid on the block at *just* fifteen years old. The anniversary makes it appealing, and easily updated with the fewer new variant rules. Odds: Fairly high.
5) Dark Sun. D&D for people who hate D&D. It's distinct and can really engage with fans who are tired of the generic and know what to expect from the world. Odds: Low. Popular but you *need* psionics and new races and a lot more room to expand on how each race is different and how the world works. Plus alternate rules like bone weapons, defiling, wild talents, elemental priests, etc. To say nothing about an entire bestiary of new creatures...
6) Al Qadim. Arabic Adventures. Tales of 1001 Nights, the world. Technically already open and available on the Guild, but might be neat to give it a signal boost. It's traditional fantasy, but very different. Odds: Low, as it's technically already available. And has some cultural appropriation elements now.
7) Spelljammer. I love the quirkiness of this setting, but the funky rules and limitations placed on things made it awkward at low levels. You *needed* a high level caster. And not everyone likes the idea of space in their campaign setting being, well, space. Reimagining this setting as on the Astral Sea might work better, with the "crystal spheres" being portals to worlds in the Material Plane. Odds: Lower. This feels like a good option for the second or third set of settings.
8) Greyhawk. The classic but very similar to the Realms. I find the world bland and lacking in good story hooks personally. But it's also more open to DM customisation. Odds: Medium. I think they might go for more different and odd settings first before providing more generic settings.
9) Kara Tur. I think there's room for some fun Wuxia campaigns and the reminder to new players that you don't *have* to play Western fantasy. Odds: Low, as already on the Guild.
10. Maztica. A neat idea of colonial South America mixed with fantasy. I don't know much about it. Odds: Super low. Never really popular, and technically part of the Guild already as it's in the Realms. And the colonial aspect and real world analogies have some nasty cultural appropriation implications.
11) Mystara. I know very little about this world. The Hollow World aspect is neat, but this feels like a separate sub-setting. Odds: See "Greyhawk". Different but not different enough. I imagine the "no gods" thing might be interesting for some. It's probably easier to do than Greyhawk, honestly.
12) Birthright. Another setting I only know tangentially. It's neat, but would require some Mass Combat rules and kingdom management to play properly. Odds: Low at this time, since we haven't seen any of the content in UA to playtest.
13) Council of Wyrms. Less a setting and more a hook for playing dragons. Odds: Super low. Not a good choice since balancing dragons would be hard and we haven't seen a dragon class in UA.
14) Blackmoore. The first campaign setting. Odds: Zero. The rights were retained by Arneson who used them with Zeitgeist Games and published by Goodman Games. I doubt WotC can touch them.
(Similar things can be said about Dragon Fist (sold to Green Ronin), Lankhman, and Kalamar.)
15) Nentir Vale. Originally, this was supposed to be in the Realms. They just changed the proper names when they decided not to make FR the default setting of 4e. This setting is bland. It's a mishmash of ideas created randomly by dozens of different people as books were written without planning or real forethought. The whole point was a generic world people could build into their own setting or place into whatever existing setting they're using. There's no hook, and nothing to distinguish it from every other generic fantasy world WotC does. Odds: Medium. Really, because it's so simple, they could repeat the lore pretty quickly. And it's hook of being a simple setting people can make their own still works.