Something that came to my mind:
Just a Fun Theory on Possible future scenario:
There are 5 major Crime Families ("The Big 5"), which includes the DeLucas.
The other 4 Families all despise the DeLuca Family for varying reasons and degrees.
One day, the Mysterious 6, secret organization led by MC's father contacts each Head of the Family (the Dons), and as TundraLupus mentioned above, the 4 Families and the Mysterious 6 form a secret alliance and launch a simultaneous attack from all sides (which literally shocks everyone, including Wilfred, Cordia and Gracie).
The DeLucas barely hang on, with help of some of their allies (minor Families), and their own Capos, Elite Soldados, and especially the 4 Serpents, but the Mysterious 6 lure each of the Serpents into a trap.
Each Serpent fights valiantly (taking down many enemies before falling), but eventually falls.
- "Serpent": after killing countless foes, eventually encounters and fights MC's father. It is an emotional battle, which lasts a long time (and is a close battle), but is defeated. MC's father points the gun at his head & says "Any last words?" "Serpent"'s reply is "Your son is a good man, something you will never be, and you'll fall by his hands.". Afterwards, shot is fired.
- Gottardo: he fights 2 vs 1 against the two members of mysterious 6. He manages to kill one of them, but is killed by the other one. Gottardo's last words "Damn, just when things were getting fun." But he was smiling as he went.
- Cynthia: it is her last dance of death. She fights a member of the Mysterious 6, and manages to kill her opponent after a long battle. However, afterwards due to her many injuries, she slumps and dies.
- 4th Serpent: like Gottardo, he fight against the two members of mysterious 6, 2 vs 1. He fights a good battle, but unfortunately unlike Gottardo, he is overwhelmed by his opponents and is killed.
After the fall of the Serpents, the tide of the battle turns in favor of the Mysterious 6 & the Big 4 Families, and the DeLucas start losing ground.
There have been some theories out there that Serpents may also betray the DeLucas. But I always was of the mind that I'd prefer the Serpents to stay loyal to the Family and perhaps go out in a blaze of glory.
Things may or may not happen like the above.
But regardless, I find it quite fun to theorize what might happen.
Not gonna lie, the "secret alliance" between Mysterious 6 & the 4 major Crime Families against the DeLucas give it the whole Legion of Doom/Injustice League feel.