Of all the theories Kitase debunked, the connection between Final Fantasy VII and X remain intact. According to Kitase:
“I won’t completely come out and say that it is the same world,” said Kitase. “However, Shinra in FFX-2 was created by [Kazushige] Nojima, the scenario writer, and when he thought him up, he thought it might be good if people would imagine that after a few years after the story of Final Fantasy X-2, that person Shinra will grow up and start the Shinra company. So that is something that he did hint in there. That being said, I’m not gonna say that it’s the same.”
However, the connection might as well be canon at this point. According to the Ultimania:
In Final Fantasy X-2, a member of the Gullwings named “Shinra” proposes the concept of extracting the life energy from within the planet Spira. In the Final Fantasy X-2 Ultimania guidebook published by Square Enix, Final Fantasy VII and Final Fantasy X-2 scenario writer Kazushige Nojima stated that the character Shinra and his proposal are a deliberate nod to the Shinra Company of Final Fantasy VII, and also revealed that he envisioned the events of Final Fantasy X-2 as a prequel to those in Final Fantasy VII. This connection had previously been hinted toward by Kitase and lead Final Fantasy developer Yoshinori Kitase during an interview in the Final Fantasy X Ultimania Omega guidebook, and was again detailed in the Final Fantasy VII Ultimania Omega — two other official publications of Square Enix.
So then what does this mean for the series?
First, Shinra, the Al-Bhed boy, sets in motion the catalyst for most of Final Fantasy VII. But due to his discovery, other Al-Bhed entrepreneurs would travel from Spira to Gaia looking to strike it rich. What they bring with this is their culture, including their language. They would also bring the Al-Bhed, which would become a legitimate language rather than just a cipher. But the biggest contribution would be the Machina that would siphon Mako out of the Lifestream.
According to Wakka:
Long time ago, there were a whole lot of cities in Spira. Big cities with Machina -machines- to run ’em. People played all day and let the Machina do the work.
The Al-Bhed would no doubt like to reclaim this past. In a sense, the Al-Bhed would be indirectly responsible, yet again, for another catastrophe.
The former outcast becomes holy people, but only due to legend. The reality isn’t that they were naturally in tune with the planet, they were just really good at making Materia. Whether or not Sephiroth knows it, the Cetra, the people he believes to be, are just entrepreneurs. They aren’t really anything special.
The biggest clue that Aerith is a Cetra is his entrepreneur spirit, as she sells flowers. Of course, she got the idea from Zack. But like the Cetra, she makes money selling the Planet. Another would be her green eyes. All of the Al-Bheds have green eyes, but somewhere down the line, the spirals would dilute with every generation.