I guess maybe the reason why only Luffy has been able to awaken this mythical zoan for such a long time and no one else may be because one of the requirements to awaken this devil fruit is to take massive amounts of damage and be the edge of death many times to awaken? Maybe it requires the user to perform good deeds?
Also even before awakening, Luffy's gears clearly stretched the boundaries of what a normal Paramecia devil fruit could do before their awakening. I guess you could say that stuff like Red Hawk and smoke rings around Gear 4 Luffy were hints of the Nika Fruit, Nika being the Sun God, and Luffy being allured to having fire abilities and light being able to bend just like rubber.
This is also interesting once you consider Luffy's relations with other characters and their devil fruits.
Ace and Sabo- the Flame Flame Fruit > weaker and lesser than the Sun God fruit
Akainu- the Lava Fruit> the more destructive and damaging version of the Sun God fruit
Blackbeard- the darkness Fruit> the evil, the opposite and arch enemy to the Sun God fruit.
Sengoku- Buddha Fruit> also a human fruit, and also a god fruit
People also always speculated why Luffy is the only Paramecia fruit who's rubber abilities were always active by default, unlike other Paramecia who actually had to activate them to work. Luffy could even stretch even if his body is in water, as shown all the way back in arlong park.
And since Luffy's ship is the Thousand Sunny, it would really fit the vessel of the Sun God Nika. Luffy's body was also glowing like the sun while he was unconscious in the water after being beaten by Kaido.
People can argue whether they like this direction that Oda took or if it's even a asspull, but at least the hints of Nika were always there and isn't completely baseless or groundless.
I'm more interested in knowing what new hax abilites Luffy will get after the awakening, since mythical zoans always come with elemental abilities + hax abilities.
Marco can regenerate, kaido can fly and can use the three elements of wind/fire/lightning, Sengoku can shoot laser beams, Yamato has ice flame and ice armor.
I wonder what unique and hax abilities Luffy will get?