After Black Panther: Wakanda Forever revealed the hidden undersea kingdom of Talokan, there is a strong possibility that more hidden locations are going to be revealed in the Marvel Cinematic Universe. Wakanda was introduced in 2018 in Black Panther as another nation in hiding, which means that so far, the MCU has started to develop two off-the-grid nations within their universe. But, according to the comics, there are many more nations that have yet to be explored and that could be tweaked to fit the MCU perfectly.
Even though some nations are not hidden in the comics or are hidden in plain sight, it could lead to interesting and intricate storylines within the MCU that can help expand the universe. For example, the underwater city of Talokan is as intricate as any physical location in the real world and added another layer of depth to the MCU. It is unlikely Marvel Studios is going to slow down anytime soon with adding new locations to the MCU, and there are places with the potential to make an appearance sooner rather than later.
Attilan
If and when the MCU decides to introduce the Inhumans (outside a Multiverse of Madness cameo), it is likely that Attilan will be introduced as well. It is a city that the Inhumans settled in thousands of years ago, according to the Marvel Comics. Its location has varied from different spots on Earth, to floating in the sky, to even on the moon, and it is hidden from mortal humans intentionally. The MCU hasn't made it clear if Inhumans will be part of the MCU, but if they are down the line, Attilan will likely join.
In the present day of Marvel, Attilan is known as The Great Refuge by world leaders. That's because the Fantastic Four discovered it and exposed the location it resided in at the time. That means that if the MCU has any intention of bringing the Inhumans into the MCU soon, the upcoming Fantastic Four movie could provide an optimal storyline that may even reveal Attilan as the next hidden nation in the MCU.
Bagalia
Bagalia is an island nation in Marvel Comics that is a safe haven run by villains for villains. Baron Zemo runs the nation, and since he returned in The Falcon and the Winter Soldier, Zemo may appear again in Thunderbolts or another upcoming MCU project. Later on in the comics, Taskmaster joins forces with Zemo to help run the hidden nation to help conceal the world's supervillains and give them a secret hideout.
Since Taskmaster's next known appearance is in the Thunderbolts, and she is portrayed as an anti-hero in that gang, it will be interesting to see if this location ever makes an MCU appearance. The MCU is known for switching things up, so it's possible that Zemo could be running the show on his own and Taskmaster actually works against him, perhaps to expose the villains' hideout. After the powerful Taskmaster suffered in Black Widow at the hands of the Red Room, it would make sense for her to want to take down another villainous nation.
Genosha
While Genosha isn't a hidden nation in the comics, it could be tweaked in the MCU to explain where the X-Men have been when Marvel Studios decides to formally introduce them. Like Wakanda, it is a fictional country, in this case located northeast of Madagascar. Also, similar to Wakanda, it boasts prosperity, wealth, and high living standards for its citizens, although that is where the similarities end. Genosha has a darker undertone than many fictional nations in the Marvel world, but it could also be used as a backdrop for a powerful story.
Genosha was built and thrived off of the backs of mutants who were captured and enslaved, then exploited for their unique abilities. If the MCU wanted to find a way to organically integrate the X-Men into the cinematic universe without banking on X-Men nostalgia, Genosha would be an excellent way to do it. If the X-Men had been slaves of Genosha with no real knowledge of the outside world or current events, it would explain why they never showed up to save the world. It could also make for an empowering story about humanity and respecting each other's differences.
Krakoa
While it was thought that the comment in Avengers: Endgame about underwater volcanoes was referring to Atlantis (now officially known as Talokan), it's possible that the MCU was actually setting up Krakoa. Krakoa is a Pacific Island that is actually a mutant itself. When the Avengers detected underwater volcanoes, it could have been that they were actually detecting the movement or even the "birth" of Krakoa.
The MCU must fix X-Men issues from the past, and this self-contained story could fit well into the MCU while introducing Krakoa as the next no-longer-hidden-location. The comic storyline of Krakoa could make for a good first X-men movie in the MCU, as the X-men travel to the island to investigate strong readings of a present mutant life form. What they don't realize is that Krakoa itself is the mutant that will eventually serve as a host nation for all mutants worldwide.
Latveria
Latveria is a nation very similar to Wakanda, a physical country that may not exist in the real world but takes up space on planet Earth within Marvel Comics. It is not exactly hidden or concealed the way Talokan or Attilan is, but instead, it is a physical country that has simply kept a low profile. It is a nation ruled by Doctor Doom, and he bounces between villain and cautious anti-hero depending on how events will affect his nation.
Before the announcement that Doctor Doom would not be the villain in the upcoming Fantastic Four movie, Latveria would have been a reasonable guess as to the next hidden nation to appear in the MCU. However, there's no reason that Doom and Lateveria couldn't appear in the background of other MCU projects as the villain is slowly built up as a threat. Doom may want the country to lie low as he amasses power before ultimately striking out. Regardless, it appears that there are a lot more lands to explore in the Marvel Cinematic Universe, and Black Panther: Wakanda Forever's Talokan was just the tip of the iceberg.
