I saw a post somewhere, I thought it was in that topic, I don't know. Anyways, this post by someone I can't remember who it was, had parts of interviews with Nomura and some other Square people along with bits of parts in the X-2 game that alluded to 7 (ex. ShinRa's infamous comment about harnessing the planet's energy). Anyways, in these interviews, Nomura said that yes, 7 and X were connected, with X being a prequel to 7. Rin teamed up with ShinRa to attempt to harness the planet's energy (though this did, as ShinRa said, take many generations). Eventually (after space travel was acquired) ShinRa's descendents went to another planet (the Planet in 7) and set up the ShinRa company there. That was the gist of it I think. So yes, according to Nomura and some other people (Kitase I think and the Ultimania guides), 7 and X are connected. If I remembered where I saw that post I'd give you the link, but I can't, sorry, I could have sworn it was in that topic.