Luffy fruit and all about him
Luffy Is A Mythical Monkey Man, Not A Rubber Man
This theory will try to explain the connection between Zunesha, Luffy and what the Gorosei were talking about the mysterious devil fruit thah the World Goverment had changed its name.
Luffy real devil fruit is not Gomu Gomu No Mi (paramecia), its really a mythical zoan called "Saru Saru No Mi Model Hanuman" (Monkey Monkey Fruit Model Hanuman)
Ok, lets me explain. It has lots to do with Hindu Myhtology, and i'm not an expert in those field but i will try my best.
The name Zunesha was adopted from Ganesha, the gods of prosperity and wisdom. He is also known as "The Lord Of The People" and "The Remover Of Obstacles" which kinda foreshadow the motive of Zunesha arrival in the latest chapter.
In the old mythology Hanuman have a strong connection with Ganesha, hence Zunesha also share some connection with Luffy.
There is many possibility why Zunesha arrived at Wano. Maybe to protect The Minks tribe who Zunesha has considered as "his people". Or maybe there is another possibility. Zunesha detected something, or rather Someone.
I believe Gorosei was informed about the arrival of Zunesha. And they actually knew the connection between Zunesha and the mysterious devil fruit. Thats why they were shocked by Zunesha action or rather Reaction.
Zunesha came to Wano because he is reacting to the awekening of Hanuman.
Hanuman is the real nature of Gomu Gomu No Mi., and luffy is in the process of awakening it and discovering the truth.
Oda once said that he is a big fan of Akira Toriyama's Dragon Ball and One Piece is partly inspired by his favourite Manga. As we all know, Son Goku is loosely adapted from Journey Of The West's main character, The Monkey King (Son Wukong). Journey To The West is a novel that revolve around The Mighty Monkey King and the Buddhist mythology, hence Oda adapted a Hindu mythology for his main character that also revolve about a tales of a powerful Monkey
3. Hanuman And Luffy
Hanuman and luffy share some (many) traits and backstory
Hanuman is a War General, known for his might and also his strong leadership in several war like The Battle of Lanka, leading many tribes and species to war.
This is also the case with Luffy, great leadership, leads wars, befriend anyone, can lead and motivates everybody.
Luffy is reincarnation of Joy Boy (always shown smiling).
Hanuman is reincarnation of Shiva. Shiva is known to destroy Tripura (three cities made of gold, silver and iron) with just a SMILE.
Hanuman is son of Vayu, God of Wind and Air.
Luffy is son of Dragon, although never shown but many believe have some sort of devil fruit that can control air/cloud/storm.
Hanumon once thought the sun is a golden color fruit, then try to reach the sky to obtain the sun. He is later stopped and punished by Indra, the god of storm
Luffy once reached the sky, found the golden Bell fought Enel along the way who believed he is the god of storm.
Hanuman was once caught when he tries to save Sita, wife of Ramayana. When the enemy try to burn his tail, Hanuman evades the fire by changing the length of his limb.
Luffy obviously can stretch his limbs. The goverment use this as a coverup and said hanuman fruit is just a rubber fruit. Maybe the unawakened Hanuman fruit only got access to this one ability.
4. Sun God Nika, Joyboy and Luffy is connected
As previously stated, Hanuman once tries to eat the sun. Luffy never tries this, but a very long time ago a certain person maybe.
Sun God Nika seemed to be a lanky, warrior-like figure with "Noodly Limbs" and flame-shaped hair. He is said to be the leader of slaves that will one day bring "smiles" to them. His image is clearly smiling and looks like a joyful person. Nika once attempt to do something with the sun, or got some power related to fire/heat, got famous for it and later called as the Sun God Nika.
Noodly limbs could also imply that Nika is the previous owner of the Gomu Gomu/Hanuman fruit.
Back to Hanuman story, after he is caught trying to obtain the sun, he got punished and sustained an injury on his body. His father go on a strike and blocked the air from all living creature. The gods needs Vayu to calm down or all living things will die without air. They healad Hanuman, but also give him some boons which is resistant towards LIGHTNING and FIRE.
On the other hand Luffy try to take the Sun for himself (Ace the Mera Mera No Mi), punished by the magma, got a permanent injury on his chest, and later developed a fire attack and he is resistant to his own FIRE. As we all knew Luffy is already resistant towards LIGHTNING.
5. Memory Erased
Hanuman memory was once erased by the higher gods, because he is kinda mischief and displeased the gods. He forgot about his real strength and capability for a while.
The Hanuman fruit real name and powered is erased by the higher hands because of something the previous owner may had done to the Higher Goverment and Luffy never knew his real strength and his fruit capability.
Luffy real devil fruit is not Gomu Gomu No Mi, its
Saru Saru No Mi Model Hanuman
a really rare powerful mythical zoan which the previous owner wrecks the old ruling government.
Edit: I missed a detail about the tragedy after Impel
"Hanuman leap for the sun proves to be fatal and he is burnt to ashes from the sun's heat. His ashes fall onto the earth and oceans. Gods then gather the ashes and his bones from land and, with the help of FISHES, re-assemble him."
(Hanuman's Tale: The Messages of a Divine Monkey. Oxford University Press. )
This happens to luffy after impel, luffy got burned by magma, lost his bro (fire), lost his will to live, until a certain fishman brought him back to life.