
In the timeline of Black Panther: Wakanda Forever (2024), Nakia left her homeland 6 years ago, abandoning her espionage career to settle in Haiti. This 6-year period includes the aftermath of Thanos' snap in Avengers: Infinity War and Avengers: Endgame. Therefore, Toussaint likely came into existence around late 2018 or early 2019.
Another noteworthy point is that Toussaint's real name in Wakandan is T’Challa, just like his father.
Explaining the identity of T’Challa's son in the comic's original storyline
In the main Marvel universe, T’Challa doesn't have a son. However, in alternate realities, he, along with his long-time partner Ororo Munroe/Storm, has many children, with the most prominent being Azari T’Challa.
Unlike other characters who always debut in comic panels, Azari first appeared in the animated film Next Avengers: Heroes of Tomorrow (2008). Set in a dystopian future, the Avengers are slaughtered by Ultron in this movie.
Later, Azari collaborated with his superhero peers to resist Ultron. Two years later, T’Challa's son was introduced into the Marvel comic storyline in Avengers #1.

Nevertheless, Azari and Toussaint share few similarities, if any, except for their names based on their respective fathers. Azari's mother is Storm, a prominent member of the X-Men. This implies that he is also a mutant, possessing the power to control lightning like his mother and a physique similar to his father.
On the other hand, Toussaint, at least at the current moment, seems to be just a regular boy with no superpowers. This suggests that he is seemingly a completely new character, created by Marvel specifically for the MCU and not based on any existing imagery.
The Future of Toussaint in the MCU
Despite not wanting her son to bear the burden of royal responsibility, Nakia always wishes to preserve Toussaint's tribal roots. That's why when introducing the boy to Shuri, she said, ' Prince T’Challa, son of King T’Challa .'
Currently, Wakanda's throne has been passed on to M'Baku by Shuri. However, since M'Baku values T’Challa's family highly, it's not ruled out that he might be willing to pass the throne to Toussaint in the future, instead of passing it down to his own descendants. After all, what M'Baku cares about the most is peace, unity, and the development of Wakanda, rather than power or position.

Regarding the superhero role, Toussaint could potentially become the new Black Panther of the MCU in the distant future. Shuri has found a way to recreate the Heart-Shaped Herb - the herb that grants superhuman physical strength to Wakandans to become the Black Panther and bear the responsibility of protecting their homeland. Additionally, as a mentor figure, it's not excluded that Shuri might guide Toussaint on his journey to become the new guardian of Wakanda.
More importantly, in recent years, Marvel Studios has been nurturing plans for a young superhero team to prepare for the future of the MCU, featuring notable names like Kate Bishop, Elijah Bradley, Tommy & Billy, America Chavez, Kid Loki, Kamala Khan, and soon to come, Riri Williams.

In the coming years, as Toussaint matures, he could seamlessly assume the role of Black Panther from Shuri. Alongside these characters, they could form a new superhero team. Toussaint's appearance in Black Panther: Wakanda Forever, paying homage to Chadwick Boseman, might serve as a foundation for Marvel Studios to continue its future projects.
Source: ScreenRant, Marvel, Den of Geek